Unisender Go: new ESP

Add support for Unisender Go --------- Co-authored-by: Mike Edmunds <medmunds@gmail.com>
2025-12-20 03:41:05 -05:00 · 2024-03-05 22:38:40 +03:00
parent a2c0ed6817
commit a71a0d9af8
15 changed files with 2477 additions and 20 deletions
--- a/.github/workflows/integration-test.yml
+++ b/.github/workflows/integration-test.yml
@@ -50,6 +50,7 @@ jobs:
          - { tox: django41-py310-sendgrid, python: "3.10" }
          - { tox: django41-py310-sendinblue, python: "3.10" }
          - { tox: django41-py310-sparkpost, python: "3.10" }
+          - { tox: django41-py310-unisender_go, python: "3.10" }

    steps:
      - name: Get code
@@ -97,3 +98,7 @@ jobs:
          ANYMAIL_TEST_SENDINBLUE_DOMAIN: ${{ secrets.ANYMAIL_TEST_SENDINBLUE_DOMAIN }}
          ANYMAIL_TEST_SPARKPOST_API_KEY: ${{ secrets.ANYMAIL_TEST_SPARKPOST_API_KEY }}
          ANYMAIL_TEST_SPARKPOST_DOMAIN: ${{ secrets.ANYMAIL_TEST_SPARKPOST_DOMAIN }}
+          ANYMAIL_TEST_UNISENDER_GO_API_KEY: ${{ secrets.ANYMAIL_TEST_UNISENDER_GO_API_KEY }}
+          ANYMAIL_TEST_UNISENDER_GO_API_URL: ${{ vars.ANYMAIL_TEST_UNISENDER_GO_API_URL }}
+          ANYMAIL_TEST_UNISENDER_GO_DOMAIN: ${{ vars.ANYMAIL_TEST_UNISENDER_GO_DOMAIN }}
+          ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID: ${{ vars.ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID }}
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -35,9 +35,14 @@ Features

 * **Brevo:** Add support for batch sending
  (`docs <https://anymail.dev/en/latest/esps/brevo/#batch-sending-merge-and-esp-templates>`__).
+
 * **Resend:** Add support for batch sending
  (`docs <https://anymail.dev/en/latest/esps/resend/#batch-sending-merge-and-esp-templates>`__).

+* **Unisender Go**: Add support for this ESP
+  (`docs <https://anymail.dev/en/latest/esps/unisender_go/>`__).
+  (Thanks to `@Arondit`_ for the implementation.)
+

 v10.2
 -----
@@ -1572,6 +1577,7 @@ Features
 .. _@ailionx: https://github.com/ailionx
 .. _@alee: https://github.com/alee
 .. _@anstosa: https://github.com/anstosa
+.. _@Arondit: https://github.com/Arondit
 .. _@b0d0nne11: https://github.com/b0d0nne11
 .. _@calvin: https://github.com/calvin
 .. _@chrisgrande: https://github.com/chrisgrande
--- a/README.rst
+++ b/README.rst
@@ -37,6 +37,7 @@ Anymail currently supports these ESPs:
 * **Resend**
 * **SendGrid**
 * **SparkPost**
+* **Unisender Go**

 Anymail includes:

--- a/anymail/backends/unisender_go.py
+++ b/anymail/backends/unisender_go.py
@@ -0,0 +1,343 @@
+from __future__ import annotations
+
+import re
+import typing
+import uuid
+from datetime import datetime, timezone
+from email.charset import QP, Charset
+from email.headerregistry import Address
+
+from django.core.mail import EmailMessage
+from requests import Response
+from requests.structures import CaseInsensitiveDict
+
+from anymail.backends.base_requests import AnymailRequestsBackend, RequestsPayload
+from anymail.message import AnymailRecipientStatus
+from anymail.utils import Attachment, EmailAddress, get_anymail_setting, update_deep
+
+# Used to force RFC-2047 encoded word
+# in address formatting workaround
+QP_CHARSET = Charset("utf-8")
+QP_CHARSET.header_encoding = QP
+
+
+class EmailBackend(AnymailRequestsBackend):
+    """Unisender Go v1 Web API Email Backend"""
+
+    esp_name = "Unisender Go"
+
+    def __init__(self, **kwargs: typing.Any):
+        """Init options from Django settings"""
+        esp_name = self.esp_name
+
+        self.api_key = get_anymail_setting(
+            "api_key", esp_name=esp_name, kwargs=kwargs, allow_bare=True
+        )
+
+        self.generate_message_id = get_anymail_setting(
+            "generate_message_id", esp_name=esp_name, kwargs=kwargs, default=True
+        )
+
+        # No default for api_url setting -- it depends on account's data center. E.g.:
+        # - https://go1.unisender.ru/ru/transactional/api/v1
+        # - https://go2.unisender.ru/ru/transactional/api/v1
+        api_url = get_anymail_setting("api_url", esp_name=esp_name, kwargs=kwargs)
+        if not api_url.endswith("/"):
+            api_url += "/"
+
+        # Undocumented setting to control workarounds for Unisender Go display-name issues
+        # (see below). If/when Unisender Go fixes the problems, you can disable Anymail's
+        # workarounds by adding `"UNISENDER_GO_WORKAROUND_DISPLAY_NAME_BUGS": False`
+        # to your `ANYMAIL` settings.
+        self.workaround_display_name_bugs = get_anymail_setting(
+            "workaround_display_name_bugs",
+            esp_name=esp_name,
+            kwargs=kwargs,
+            default=True,
+        )
+
+        super().__init__(api_url, **kwargs)
+
+    def build_message_payload(
+        self, message: EmailMessage, defaults: dict
+    ) -> UnisenderGoPayload:
+        return UnisenderGoPayload(message=message, defaults=defaults, backend=self)
+
+    # Map Unisender Go "failed_email" code -> AnymailRecipientStatus.status
+    _unisender_failure_status = {
+        # "duplicate": ignored (see parse_recipient_status)
+        "invalid": "invalid",
+        "permanent_unavailable": "rejected",
+        "temporary_unavailable": "failed",
+        "unsubscribed": "rejected",
+    }
+
+    def parse_recipient_status(
+        self, response: Response, payload: UnisenderGoPayload, message: EmailMessage
+    ) -> dict:
+        """
+        Response example:
+        {
+          "status": "success",
+          "job_id": "1ZymBc-00041N-9X",
+          "emails": [
+            "user@example.com",
+            "email@example.com",
+          ],
+          "failed_emails": {
+            "email1@gmail.com": "temporary_unavailable",
+            "bad@address": "invalid",
+            "email@example.com": "duplicate",
+            "root@example.org": "permanent_unavailable",
+            "olduser@example.net": "unsubscribed"
+          }
+        }
+        """
+        parsed_response = self.deserialize_json_response(response, payload, message)
+        # job_id serves as message_id when not self.generate_message_id
+        job_id = parsed_response.get("job_id")
+        succeed_emails = {
+            recipient: AnymailRecipientStatus(
+                message_id=payload.message_ids.get(recipient, job_id), status="queued"
+            )
+            for recipient in parsed_response["emails"]
+        }
+        failed_emails = {
+            recipient: AnymailRecipientStatus(
+                # Message wasn't sent to this recipient, so Unisender Go hasn't stored
+                # any metadata (including message_id)
+                message_id=None,
+                status=self._unisender_failure_status.get(status, "failed"),
+            )
+            for recipient, status in parsed_response.get("failed_emails", {}).items()
+            if status != "duplicate"  # duplicates are in both succeed and failed lists
+        }
+        return {**succeed_emails, **failed_emails}
+
+
+class UnisenderGoPayload(RequestsPayload):
+    # Payload: see https://godocs.unisender.ru/web-api-ref#email-send
+
+    data: dict
+
+    def __init__(
+        self,
+        message: EmailMessage,
+        defaults: dict,
+        backend: EmailBackend,
+        *args: typing.Any,
+        **kwargs: typing.Any,
+    ):
+        self.generate_message_id = backend.generate_message_id
+        self.message_ids = CaseInsensitiveDict()  # recipient -> generated message_id
+
+        http_headers = kwargs.pop("headers", {})
+        http_headers["Content-Type"] = "application/json"
+        http_headers["Accept"] = "application/json"
+        http_headers["X-API-KEY"] = backend.api_key
+        super().__init__(
+            message, defaults, backend, headers=http_headers, *args, **kwargs
+        )
+
+    def get_api_endpoint(self) -> str:
+        return "email/send.json"
+
+    def init_payload(self) -> None:
+        self.data = {  # becomes json
+            "headers": CaseInsensitiveDict(),
+            "recipients": [],
+        }
+
+    def serialize_data(self) -> str:
+        if self.generate_message_id:
+            self.set_anymail_id()
+
+        headers = self.data["headers"]
+        if self.is_batch():
+            # Remove the all-recipient "to" header for batch sends.
+            # Unisender Go will construct a single-recipient "to" for each recipient.
+            # Unisender Go doesn't allow a "cc" header without an explicit "to"
+            # header, so we cannot support "cc" for batch sends.
+            headers.pop("to", None)
+            if headers.pop("cc", None):
+                self.unsupported_feature(
+                    "cc with batch send (merge_data or merge_metadata)"
+                )
+
+        if not headers:
+            del self.data["headers"]  # don't send empty headers
+
+        return self.serialize_json({"message": self.data})
+
+    def set_anymail_id(self) -> None:
+        """Ensure each personalization has a known anymail_id for event tracking"""
+        for recipient in self.data["recipients"]:
+            # This ensures duplicate recipients get same anymail_id
+            # (because Unisender Go only sends to first instance of duplicate)
+            email_address = recipient["email"]
+            anymail_id = self.message_ids.get(email_address) or str(uuid.uuid4())
+            recipient.setdefault("metadata", {})["anymail_id"] = anymail_id
+            self.message_ids[email_address] = anymail_id
+
+    #
+    # Payload construction
+    #
+
+    def set_from_email(self, email: EmailAddress) -> None:
+        self.data["from_email"] = email.addr_spec
+        if email.display_name:
+            self.data["from_name"] = email.display_name
+
+    def _format_email_address(self, address):
+        """
+        Return EmailAddress address formatted for use with Unisender Go to/cc headers.
+
+        Works around a bug in Unisender Go's API that rejects To or Cc headers
+        containing commas, angle brackets, or @ in any display-name, despite those
+        names being properly enclosed in "quotes" per RFC 5322. Workaround substitutes
+        an RFC 2047 encoded word, which avoids the problem characters.
+
+        Note that parens, quote chars, and other special characters appearing
+        in "quoted strings" don't cause problems. (Unisender Go tech support
+        has confirmed the problem is limited to , < > @.)
+
+        This workaround is only necessary in the To and Cc headers. Unisender Go
+        properly formats commas and other characters in `to_name` and `from_name`.
+        (But see set_reply_to for a related issue.)
+        """
+        formatted = address.address
+        if self.backend.workaround_display_name_bugs:
+            # Workaround: force RFC-2047 QP encoded word for display_name if it has
+            # prohibited chars (and isn't already encoded in the formatted address)
+            display_name = address.display_name
+            if re.search(r"[,<>@]", display_name) and display_name in formatted:
+                formatted = str(
+                    Address(
+                        display_name=QP_CHARSET.header_encode(address.display_name),
+                        addr_spec=address.addr_spec,
+                    )
+                )
+        return formatted
+
+    def set_recipients(self, recipient_type: str, emails: list[EmailAddress]):
+        for email in emails:
+            recipient = {"email": email.addr_spec}
+            if email.display_name:
+                recipient["substitutions"] = {"to_name": email.display_name}
+            self.data["recipients"].append(recipient)
+
+        if emails and recipient_type in {"to", "cc"}:
+            # Add "to" or "cc" header listing all recipients of type.
+            # See https://godocs.unisender.ru/cc-and-bcc.
+            # (For batch sends, these will be adjusted later in self.serialize_data.)
+            self.data["headers"][recipient_type] = ", ".join(
+                self._format_email_address(email) for email in emails
+            )
+
+    def set_subject(self, subject: str) -> None:
+        if subject:
+            self.data["subject"] = subject
+
+    def set_reply_to(self, emails: list[EmailAddress]) -> None:
+        # Unisender Go only supports a single address in the reply_to API param.
+        if len(emails) > 1:
+            self.unsupported_feature("multiple reply_to addresses")
+        if len(emails) > 0:
+            reply_to = emails[0]
+            self.data["reply_to"] = reply_to.addr_spec
+            display_name = reply_to.display_name
+            if display_name:
+                if self.backend.workaround_display_name_bugs:
+                    # Unisender Go doesn't properly "quote" (RFC 5322) a `reply_to_name`
+                    # containing special characters (comma, parens, etc.), resulting
+                    # in an invalid Reply-To header that can cause problems when the
+                    # recipient tries to reply. (They *do* properly handle special chars
+                    # in `to_name` and `from_name`; this only affects `reply_to_name`.)
+                    if reply_to.address.startswith('"'):  # requires quoted syntax
+                        # Workaround: force RFC-2047 encoded word
+                        display_name = QP_CHARSET.header_encode(display_name)
+                self.data["reply_to_name"] = display_name
+
+    def set_extra_headers(self, headers: dict[str, str]) -> None:
+        self.data["headers"].update(headers)
+
+    def set_text_body(self, body: str) -> None:
+        if body:
+            self.data.setdefault("body", {})["plaintext"] = body
+
+    def set_html_body(self, body: str) -> None:
+        if body:
+            self.data.setdefault("body", {})["html"] = body
+
+    def add_alternative(self, content: str, mimetype: str):
+        if mimetype.lower() == "text/x-amp-html":
+            if "amp" in self.data.get("body", {}):
+                self.unsupported_feature("multiple amp-html parts")
+            self.data.setdefault("body", {})["amp"] = content
+        else:
+            super().add_alternative(content, mimetype)
+
+    def add_attachment(self, attachment: Attachment) -> None:
+        name = attachment.cid if attachment.inline else attachment.name
+        att = {
+            "content": attachment.b64content,
+            "type": attachment.mimetype,
+            "name": name or "",  # required - submit empty string if unknown
+        }
+        if attachment.inline:
+            self.data.setdefault("inline_attachments", []).append(att)
+        else:
+            self.data.setdefault("attachments", []).append(att)
+
+    def set_metadata(self, metadata: dict[str, str]) -> None:
+        self.data["global_metadata"] = metadata
+
+    def set_send_at(self, send_at: datetime | str) -> None:
+        try:
+            # "Date and time in the format “YYYY-MM-DD hh:mm:ss” in the UTC time zone."
+            # If send_at is a datetime, it's guaranteed to be aware, but maybe not UTC.
+            # Convert to UTC, then strip tzinfo to avoid isoformat "+00:00" at end.
+            send_at_utc = send_at.astimezone(timezone.utc).replace(tzinfo=None)
+            send_at_formatted = send_at_utc.isoformat(sep=" ", timespec="seconds")
+            assert len(send_at_formatted) == 19
+        except (AttributeError, TypeError):
+            # Not a datetime - caller is responsible for formatting
+            send_at_formatted = send_at
+        self.data.setdefault("options", {})["send_at"] = send_at_formatted
+
+    def set_tags(self, tags: list[str]) -> None:
+        self.data["tags"] = tags
+
+    def set_track_clicks(self, track_clicks: typing.Any):
+        self.data["track_links"] = 1 if track_clicks else 0
+
+    def set_track_opens(self, track_opens: typing.Any):
+        self.data["track_read"] = 1 if track_opens else 0
+
+    def set_template_id(self, template_id: str) -> None:
+        self.data["template_id"] = template_id
+
+    def set_merge_data(self, merge_data: dict[str, dict[str, str]]) -> None:
+        if not merge_data:
+            return
+        assert self.data["recipients"]  # must be called after set_to
+        for recipient in self.data["recipients"]:
+            recipient_email = recipient["email"]
+            if recipient_email in merge_data:
+                # (substitutions may already be present with "to_email")
+                recipient.setdefault("substitutions", {}).update(
+                    merge_data[recipient_email]
+                )
+
+    def set_merge_global_data(self, merge_global_data: dict[str, str]) -> None:
+        self.data["global_substitutions"] = merge_global_data
+
+    def set_merge_metadata(self, merge_metadata: dict[str, str]) -> None:
+        assert self.data["recipients"]  # must be called after set_to
+        for recipient in self.data["recipients"]:
+            recipient_email = recipient["email"]
+            if recipient_email in merge_metadata:
+                recipient["metadata"] = merge_metadata[recipient_email]
+
+    def set_esp_extra(self, extra: dict) -> None:
+        update_deep(self.data, extra)
--- a/anymail/urls.py
+++ b/anymail/urls.py
@@ -23,6 +23,7 @@ from .webhooks.sparkpost import (
    SparkPostInboundWebhookView,
    SparkPostTrackingWebhookView,
 )
+from .webhooks.unisender_go import UnisenderGoTrackingWebhookView

 app_name = "anymail"
 urlpatterns = [
@@ -125,6 +126,11 @@ urlpatterns = [
        SparkPostTrackingWebhookView.as_view(),
        name="sparkpost_tracking_webhook",
    ),
+    path(
+        "unisender_go/tracking/",
+        UnisenderGoTrackingWebhookView.as_view(),
+        name="unisender_go_tracking_webhook",
+    ),
    # Anymail uses a combined Mandrill webhook endpoint,
    # to simplify Mandrill's key-validation scheme:
    path("mandrill/", MandrillCombinedWebhookView.as_view(), name="mandrill_webhook"),
--- a/anymail/webhooks/unisender_go.py
+++ b/anymail/webhooks/unisender_go.py
@@ -0,0 +1,123 @@
+from __future__ import annotations
+
+import json
+import typing
+from datetime import datetime, timezone
+from hashlib import md5
+
+from django.http import HttpRequest, HttpResponse
+from django.utils.crypto import constant_time_compare
+
+from anymail.exceptions import AnymailWebhookValidationFailure
+from anymail.signals import AnymailTrackingEvent, EventType, RejectReason, tracking
+from anymail.utils import get_anymail_setting
+from anymail.webhooks.base import AnymailCoreWebhookView
+
+
+class UnisenderGoTrackingWebhookView(AnymailCoreWebhookView):
+    """Handler for UniSender delivery and engagement tracking webhooks"""
+
+    # See https://godocs.unisender.ru/web-api-ref#callback-format for webhook payload
+
+    esp_name = "Unisender Go"
+    signal = tracking
+    warn_if_no_basic_auth = False  # because we validate against signature
+
+    event_types = {
+        "sent": EventType.SENT,
+        "delivered": EventType.DELIVERED,
+        "opened": EventType.OPENED,
+        "clicked": EventType.CLICKED,
+        "unsubscribed": EventType.UNSUBSCRIBED,
+        "subscribed": EventType.SUBSCRIBED,
+        "spam": EventType.COMPLAINED,
+        "soft_bounced": EventType.BOUNCED,
+        "hard_bounced": EventType.BOUNCED,
+    }
+
+    reject_reasons = {
+        "err_user_unknown": RejectReason.BOUNCED,
+        "err_user_inactive": RejectReason.BOUNCED,
+        "err_will_retry": RejectReason.BOUNCED,
+        "err_mailbox_discarded": RejectReason.BOUNCED,
+        "err_mailbox_full": RejectReason.BOUNCED,
+        "err_spam_rejected": RejectReason.SPAM,
+        "err_blacklisted": RejectReason.BLOCKED,
+        "err_too_large": RejectReason.BOUNCED,
+        "err_unsubscribed": RejectReason.UNSUBSCRIBED,
+        "err_unreachable": RejectReason.BOUNCED,
+        "err_skip_letter": RejectReason.BOUNCED,
+        "err_domain_inactive": RejectReason.BOUNCED,
+        "err_destination_misconfigured": RejectReason.BOUNCED,
+        "err_delivery_failed": RejectReason.OTHER,
+        "err_spam_skipped": RejectReason.SPAM,
+        "err_lost": RejectReason.OTHER,
+    }
+
+    http_method_names = ["post", "head", "options", "get"]
+
+    def get(
+        self, request: HttpRequest, *args: typing.Any, **kwargs: typing.Any
+    ) -> HttpResponse:
+        # Unisender Go verifies the webhook with a GET request at configuration time
+        return HttpResponse()
+
+    def validate_request(self, request: HttpRequest) -> None:
+        """
+        How Unisender GO authenticate:
+        Hash the whole request body text and replace api key in "auth" field by this hash.
+
+        So it is both auth and encryption. Also, they hash JSON without spaces.
+        """
+        request_json = json.loads(request.body.decode("utf-8"))
+        request_auth = request_json.get("auth", "")
+        request_json["auth"] = get_anymail_setting(
+            "api_key", esp_name=self.esp_name, allow_bare=True
+        )
+        json_with_key = json.dumps(request_json, separators=(",", ":"))
+
+        expected_auth = md5(json_with_key.encode("utf-8")).hexdigest()
+
+        if not constant_time_compare(request_auth, expected_auth):
+            raise AnymailWebhookValidationFailure(
+                "Unisender Go webhook called with incorrect signature"
+            )
+
+    def parse_events(self, request: HttpRequest) -> list[AnymailTrackingEvent]:
+        request_json = json.loads(request.body.decode("utf-8"))
+        assert len(request_json["events_by_user"]) == 1  # per API docs
+        esp_events = request_json["events_by_user"][0]["events"]
+        return [
+            self.esp_to_anymail_event(esp_event)
+            for esp_event in esp_events
+            if esp_event["event_name"] == "transactional_email_status"
+        ]
+
+    def esp_to_anymail_event(self, esp_event: dict) -> AnymailTrackingEvent:
+        event_data = esp_event["event_data"]
+        event_type = self.event_types.get(event_data["status"], EventType.UNKNOWN)
+        timestamp = datetime.fromisoformat(event_data["event_time"])
+        timestamp_utc = timestamp.replace(tzinfo=timezone.utc)
+        metadata = event_data.get("metadata", {})
+        message_id = metadata.pop("anymail_id", event_data.get("job_id"))
+
+        delivery_info = event_data.get("delivery_info", {})
+        delivery_status = delivery_info.get("delivery_status", "")
+        if delivery_status.startswith("err"):
+            reject_reason = self.reject_reasons.get(delivery_status, RejectReason.OTHER)
+        else:
+            reject_reason = None
+
+        return AnymailTrackingEvent(
+            event_type=event_type,
+            timestamp=timestamp_utc,
+            message_id=message_id,
+            event_id=None,
+            recipient=event_data["email"],
+            reject_reason=reject_reason,
+            mta_response=delivery_info.get("destination_response"),
+            metadata=metadata,
+            click_url=event_data.get("url"),
+            user_agent=delivery_info.get("user_agent"),
+            esp_event=event_data,
+        )
--- a/docs/esps/esp-feature-matrix.csv
+++ b/docs/esps/esp-feature-matrix.csv
@@ -1,19 +1,19 @@
-Email Service Provider,:ref:`amazon-ses-backend`,:ref:`brevo-backend`,:ref:`mailersend-backend`,:ref:`mailgun-backend`,:ref:`mailjet-backend`,:ref:`mandrill-backend`,:ref:`postal-backend`,:ref:`postmark-backend`,:ref:`resend-backend`,:ref:`sendgrid-backend`,:ref:`sparkpost-backend`
-.. rubric:: :ref:`Anymail send options <anymail-send-options>`,,,,,,,,,,,
-:attr:`~AnymailMessage.envelope_sender`,Yes,No,No,Domain only,Yes,Domain only,Yes,No,No,No,Yes
-:attr:`~AnymailMessage.metadata`,Yes,Yes,No,Yes,Yes,Yes,No,Yes,Yes,Yes,Yes
-:attr:`~AnymailMessage.merge_metadata`,No,Yes,No,Yes,Yes,Yes,No,Yes,Yes,Yes,Yes
-:attr:`~AnymailMessage.send_at`,No,Yes,Yes,Yes,No,Yes,No,No,No,Yes,Yes
-:attr:`~AnymailMessage.tags`,Yes,Yes,Yes,Yes,Max 1 tag,Yes,Max 1 tag,Max 1 tag,Yes,Yes,Max 1 tag
-:attr:`~AnymailMessage.track_clicks`,No,No,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes
-:attr:`~AnymailMessage.track_opens`,No,No,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes
-:ref:`amp-email`,Yes,No,No,Yes,No,No,No,No,No,Yes,Yes
-.. rubric:: :ref:`templates-and-merge`,,,,,,,,,,,
-:attr:`~AnymailMessage.template_id`,Yes,Yes,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes
-:attr:`~AnymailMessage.merge_data`,Yes,Yes,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes
-:attr:`~AnymailMessage.merge_global_data`,Yes,Yes,(emulated),(emulated),Yes,Yes,No,Yes,No,Yes,Yes
-.. rubric:: :ref:`Status <esp-send-status>` and :ref:`event tracking <event-tracking>`,,,,,,,,,,,
-:attr:`~AnymailMessage.anymail_status`,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes
-:class:`~anymail.signals.AnymailTrackingEvent` from webhooks,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes
-.. rubric:: :ref:`Inbound handling <inbound>`,,,,,,,,,,,
-:class:`~anymail.signals.AnymailInboundEvent` from webhooks,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,No,Yes,Yes
+Email Service Provider,:ref:`amazon-ses-backend`,:ref:`brevo-backend`,:ref:`mailersend-backend`,:ref:`mailgun-backend`,:ref:`mailjet-backend`,:ref:`mandrill-backend`,:ref:`postal-backend`,:ref:`postmark-backend`,:ref:`resend-backend`,:ref:`sendgrid-backend`,:ref:`sparkpost-backend`,:ref:`unisender-go-backend`
+.. rubric:: :ref:`Anymail send options <anymail-send-options>`,,,,,,,,,,,,
+:attr:`~AnymailMessage.envelope_sender`,Yes,No,No,Domain only,Yes,Domain only,Yes,No,No,No,Yes,No
+:attr:`~AnymailMessage.metadata`,Yes,Yes,No,Yes,Yes,Yes,No,Yes,Yes,Yes,Yes,Yes
+:attr:`~AnymailMessage.merge_metadata`,No,Yes,No,Yes,Yes,Yes,No,Yes,Yes,Yes,Yes,Yes
+:attr:`~AnymailMessage.send_at`,No,Yes,Yes,Yes,No,Yes,No,No,No,Yes,Yes,Yes
+:attr:`~AnymailMessage.tags`,Yes,Yes,Yes,Yes,Max 1 tag,Yes,Max 1 tag,Max 1 tag,Yes,Yes,Max 1 tag,Yes
+:attr:`~AnymailMessage.track_clicks`,No,No,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes,Yes
+:attr:`~AnymailMessage.track_opens`,No,No,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes,Yes
+:ref:`amp-email`,Yes,No,No,Yes,No,No,No,No,No,Yes,Yes,Yes
+.. rubric:: :ref:`templates-and-merge`,,,,,,,,,,,,
+:attr:`~AnymailMessage.template_id`,Yes,Yes,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes,Yes
+:attr:`~AnymailMessage.merge_data`,Yes,Yes,Yes,Yes,Yes,Yes,No,Yes,No,Yes,Yes,Yes
+:attr:`~AnymailMessage.merge_global_data`,Yes,Yes,(emulated),(emulated),Yes,Yes,No,Yes,No,Yes,Yes,Yes
+.. rubric:: :ref:`Status <esp-send-status>` and :ref:`event tracking <event-tracking>`,,,,,,,,,,,,
+:attr:`~AnymailMessage.anymail_status`,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes
+:class:`~anymail.signals.AnymailTrackingEvent` from webhooks,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes
+.. rubric:: :ref:`Inbound handling <inbound>`,,,,,,,,,,,,
+:class:`~anymail.signals.AnymailInboundEvent` from webhooks,Yes,Yes,Yes,Yes,Yes,Yes,Yes,Yes,No,Yes,Yes,No
--- a/docs/esps/index.rst
+++ b/docs/esps/index.rst
@@ -23,6 +23,7 @@ and notes about any quirks or limitations:
   resend
   sendgrid
   sparkpost
+   unisender_go


 Anymail feature support
--- a/docs/esps/unisender_go.rst
+++ b/docs/esps/unisender_go.rst
@@ -0,0 +1,426 @@
+.. _unisender-go-backend:
+
+Unisender Go
+=============
+
+Anymail supports sending email from Django through the `Unisender Go`_ email service,
+using their `Web API`_ v1.
+
+.. _Unisender Go: https://go.unisender.ru
+.. _Web API: https://godocs.unisender.ru/web-api-ref
+
+Settings
+--------
+
+.. rubric:: EMAIL_BACKEND
+
+To use Anymail's Unisender Go backend, set:
+
+  .. code-block:: python
+
+      EMAIL_BACKEND = "anymail.backends.unisender_go.EmailBackend"
+
+in your settings.py.
+
+.. rubric:: UNISENDER_GO_API_KEY, UNISENDER_GO_API_URL
+
+.. setting:: ANYMAIL_UNISENDER_GO_API_KEY
+.. setting:: ANYMAIL_UNISENDER_GO_API_URL
+
+Required---the API key and API endpoint for your Unisender Go account or project:
+
+  .. code-block:: python
+
+      ANYMAIL = {
+          "UNISENDER_GO_API_KEY": "<your API key>",
+          # Pick ONE of these, depending on your account (go1 vs. go2):
+          "UNISENDER_GO_API_URL": "https://go1.unisender.ru/ru/transactional/api/v1/",
+          "UNISENDER_GO_API_URL": "https://go2.unisender.ru/ru/transactional/api/v1/",
+      }
+
+Get the API key from Unisender Go's dashboard under Account > Security > API key
+(Учетная запись > Безопасность > API-ключ). Or for a project-level API key, under
+Settings > Projects (Настройки > Проекты).
+
+The correct API URL depends on which Unisender Go data center registered your account.
+You must specify the full, versioned `Unisender Go API endpoint`_ as shown above
+(not just the base uri).
+
+If trying to send mail raises an API Error "User with id ... not found" (code 114),
+the likely cause is using the wrong API URL for your account. (To find which server
+handles your account, log into Unisender Go's dashboard and then check hostname
+in your browser's URL.)
+
+Anymail will also look for ``UNISENDER_GO_API_KEY`` at the
+root of the settings file if neither ``ANYMAIL["UNISENDER_GO_API_KEY"]``
+nor ``ANYMAIL_UNISENDER_GO_API_KEY`` is set.
+
+.. _Unisender Go API endpoint: https://godocs.unisender.ru/web-api-ref#web-api
+
+
+.. setting:: ANYMAIL_UNISENDER_GO_GENERATE_MESSAGE_ID
+
+.. rubric:: UNISENDER_GO_GENERATE_MESSAGE_ID
+
+Whether Anymail should generate a separate UUID for each recipient when sending
+messages through Unisender Go, to facilitate status tracking. The UUIDs are attached
+to the message as recipient metadata named "anymail_id" and available in
+:attr:`anymail_status.recipients[recipient_email].message_id <anymail.message.AnymailStatus.recipients>`
+on the message after it is sent.
+
+Default ``True``. You can set to ``False`` to disable generating UUIDs:
+
+  .. code-block:: python
+
+      ANYMAIL = {
+          ...
+          "UNISENDER_GO_GENERATE_MESSAGE_ID": False
+      }
+
+When disabled, each sent message will use Unisender Go's "job_id" as the (single)
+:attr:`~anymail.message.AnymailStatus.message_id` for all recipients.
+(The job_id alone may be sufficient for your tracking needs, particularly
+if you only send to one recipient per message.)
+
+
+.. _unisender-go-esp-extra:
+
+Additional sending options and esp_extra
+----------------------------------------
+
+Unisender Go offers a number of additional options you may want to use
+when sending a message. You can set these for individual messages using
+Anymail's :attr:`~anymail.message.AnymailMessage.esp_extra`. See the full
+list of options in Unisender Go's `email/send.json`_ API documentation.
+
+For example:
+
+.. code-block:: python
+
+    message = EmailMessage(...)
+    message.esp_extra = {
+        "global_language": "en",  # Use English text for unsubscribe link
+        "bypass_global": 1,  # Ignore system level blocked address list
+        "bypass_unavailable": 1,  # Ignore account level blocked address list
+        "options": {
+            # Custom unsubscribe link (can use merge_data {{substitutions}}):
+            "unsubscribe_url": "https://example.com/unsub?u={{subscription_id}}",
+            "custom_backend_id": 22,  # ID of dedicated IP address
+        }
+    }
+
+(Note that you do *not* include the API's root level ``"message"`` key in
+:attr:`~!anymail.message.AnymailMessage.esp_extra`, but you must include
+any nested keys---like ``"options"`` in the example above---to match
+Unisender Go's API structure.)
+
+To set default :attr:`esp_extra` options for all messages, use Anymail's
+:ref:`global send defaults <send-defaults>` in your settings.py. Example:
+
+.. code-block:: python
+
+    ANYMAIL = {
+        ...,
+        "UNISENDER_GO_SEND_DEFAULTS": {
+            "esp_extra": {
+                # Omit the unsubscribe link for all sent messages:
+                "skip_unsubscribe": 1
+            }
+        }
+    }
+
+Any options set in an individual message's
+:attr:`~anymail.message.AnymailMessage.esp_extra` take precedence
+over the global send defaults.
+
+For many of these additional options, you will need to contact Unisender Go
+tech support for approval before being able to use them.
+
+.. _email/send.json: https://godocs.unisender.ru/web-api-ref#email-send
+
+
+.. _unisender-go-quirks:
+
+Limitations and quirks
+----------------------
+
+**Attachment filename restrictions**
+  Unisender Go does not permit the slash character (``/``) in attachment filenames.
+  Trying to send one will result in an :exc:`~anymail.exceptions.AnymailAPIError`.
+
+**Restrictions on to, cc and bcc**
+  For non-batch sends, Unisender Go has a limit of 10 recipients each
+  for :attr:`to`, :attr:`cc` and :attr:`bcc`. Unisender Go does not support
+  cc-only or bcc-only messages. All bcc recipients must be in a domain
+  you have verified with Unisender Go.
+
+  For :ref:`batch sending <batch-send>` (with Anymail's
+  :attr:`~anymail.message.AnymailMessage.merge_data` or
+  :attr:`~anymail.message.AnymailMessage.merge_metadata`), Unisender Go has
+  a limit of 500 :attr:`to` recipients in a single message.
+
+  Unisender Go's API does not support :attr:`cc` with batch sending.
+  Trying to include cc recipients in a batch send will raise an
+  :exc:`~anymail.exceptions.AnymailUnsupportedFeature` error.
+  (If you've enabled :setting:`ANYMAIL_IGNORE_UNSUPPORTED_FEATURES`,
+  Anymail will handle :attr:`cc` in a Unisender Go batch send as
+  additional :attr:`to` recipients.)
+
+  With batch sending, Unisender Go effectively treats :attr:`bcc` recipients
+  as additional :attr:`to` recipients, which may not behave as you'd expect.
+  Each bcc in a batch send will be sent a *single* copy of the message,
+  with the bcc's email in the :mailheader:`To` header, and personalized using
+  :attr:`merge_data` for their own email address, if any. (Unlike some other
+  ESPs, bcc recipients in a batch send *won't* receive a separate copy of the
+  message personalized for each :attr:`to` email.)
+
+**AMP for Email**
+  Unisender Go supports sending AMPHTML email content. To include it, use
+  ``message.attach_alternative("...AMPHTML content...", "text/x-amp-html")``
+  (and be sure to also include regular HTML and text bodies, too).
+
+**Use metadata for campaign_id**
+  If you want to use Unisender Go's ``campaign_id``, set it in Anymail's
+  :attr:`~anymail.message.AnymailMessage.metadata`.
+
+**Duplicate emails ignored**
+  Unisender Go only allows an email address to be included once in a message's
+  combined :attr:`to`, :attr:`cc` and :attr:`bcc` lists. If the same email
+  appears multiple times, the additional instances are ignored. (Unisender Go
+  reports them as duplicates, but Anymail does not treat this as an error.)
+
+  Note that email addresses are case-insensitive.
+
+**Anymail's message_id is passed in recipient metadata**
+  By default, Anymail generates a unique identifier for each
+  :attr:`to` recipient in a message, and (effectively) adds this to the
+  recipients' :attr:`~anymail.message.AnymailMessage.merge_metadata`
+  with the key ``"anymail_id"``.
+
+  This feature consumes one of Unisender Go's 10 available metadata slots.
+  To disable it, see the
+  :setting:`UNISENDER_GO_GENERATE_MESSAGE_ID <ANYMAIL_UNISENDER_GO_GENERATE_MESSAGE_ID>`
+  setting.
+
+**Recipient display names are set in merge_data**
+  To include a display name ("friendly name") with a :attr:`to` email address,
+  Unisender Go's Web API uses an entry in their per-recipient template
+  "substitutions," which are also used for Anymail's
+  :attr:`~anymail.message.AnymailMessage.merge_data`.
+
+  To avoid conflicts, do not use ``"to_name"`` as a key in
+  :attr:`~anymail.message.AnymailMessage.merge_data` or
+  :attr:`~anymail.message.AnymailMessage.merge_global_data`.
+
+**No envelope sender overrides**
+  Unisender Go does not support overriding a message's
+  :attr:`~anymail.message.AnymailMessage.envelope_sender`.
+
+
+.. _unisender-go-templates:
+
+Batch sending/merge and ESP templates
+-------------------------------------
+
+Unisender Go supports :ref:`ESP stored templates <esp-stored-templates>`,
+on-the-fly templating, and :ref:`batch sending <batch-send>` with
+per-recipient merge data substitutions.
+
+To send using a template you have created in your Unisender Go account,
+set the message's :attr:`~anymail.message.AnymailMessage.template_id`
+to the template's ID. (This is a UUID found at the top of the template's
+"Properties" page---*not* the template name.)
+
+To supply template substitution data, use Anymail's
+normalized :attr:`~anymail.message.AnymailMessage.merge_data` and
+:attr:`~anymail.message.AnymailMessage.merge_global_data` message attributes.
+You can also use
+:attr:`~anymail.message.AnymailMessage.merge_metadata` to supply custom tracking
+data for each recipient.
+
+Here is an example using a template that has slots for ``{{name}}``,
+``{{order_no}}``, and ``{{ship_date}}`` substitution data:
+
+  .. code-block:: python
+
+      message = EmailMessage(
+          to=["alice@example.com", "Bob <bob@example.com>"],
+      )
+      message.from_email = None  # Use template From email and name
+      message.template_id = "0000aaaa-1111-2222-3333-4444bbbbcccc"
+      message.merge_data = {
+          "alice@example.com": {"name": "Alice", "order_no": "12345"},
+          "bob@example.com": {"name": "Bob", "order_no": "54321"},
+      }
+      message.merge_global_data = {
+          "ship_date": "15-May",
+      }
+      message.send()
+
+Any :attr:`subject` provided will override the one defined in the template.
+The message's :class:`from_email <django.core.mail.EmailMessage>` (which defaults to
+your :setting:`DEFAULT_FROM_EMAIL` setting) will override the template's default sender.
+If you want to use the :mailheader:`From` email and name defined with the template,
+be sure to set :attr:`from_email` to ``None`` *after* creating the message, as shown above.
+
+Unisender Go also supports inline, on-the-fly templates. Here is the same example
+using inline templates:
+
+  .. code-block:: python
+
+      message = EmailMessage(
+          from_email="shipping@example.com",
+          to=["alice@example.com", "Bob <bob@example.com>"],
+          # Use {{substitution}} variables in subject and body:
+          subject="Your order {{order_no}} has shipped",
+          body="""Hi {{name}},
+                  We shipped your order {{order_no}}
+                  on {{ship_date}}.""",
+      )
+      # (You'd probably also want to add an HTML body here.)
+      # The substitution data is exactly the same as in the previous example:
+      message.merge_data = {
+          "alice@example.com": {"name": "Alice", "order_no": "12345"},
+          "bob@example.com": {"name": "Bob", "order_no": "54321"},
+      }
+      message.merge_global_data = {
+          "ship_date": "May 15",
+      }
+      message.send()
+
+Note that Unisender Go doesn't allow whitespace in the substitution braces:
+``{{order_no}}`` works, but ``{{ order_no }}`` causes an error.
+
+There are two available `Unisender Go template engines`_: "simple" and "velocity."
+For templates stored in your account, you select the engine in the template's
+properties. Inline templates use the simple engine by default; you can select
+"velocity" using :ref:`esp_extra <unisender-go-esp-extra>`:
+
+  .. code-block:: python
+
+      message.esp_extra = {
+          "template_engine": "velocity",
+      }
+      message.subject = "Your order $order_no has shipped"  # Velocity syntax
+
+When you set per-recipient :attr:`~anymail.message.AnymailMessage.merge_data`
+or :attr:`~anymail.message.AnymailMessage.merge_metadata`, Anymail will use
+:ref:`batch sending <batch-send>` mode so that each :attr:`to` recipient sees
+only their own email address. You can set either of these attributes to an empty
+dict (``message.merge_data = {}``) to force batch sending for a message that
+wouldn't otherwise use it.
+
+Be sure to review the :ref:`restrictions above <unisender-go-quirks>`
+before trying to use :attr:`cc` or :attr:`bcc` with Unisender Go batch sending.
+
+.. _Unisender Go template engines: https://godocs.unisender.ru/template-engines
+
+
+.. _unisender-go-webhooks:
+
+Status tracking webhooks
+------------------------
+
+If you are using Anymail's normalized :ref:`status tracking <event-tracking>`, add
+the url in Unisender Go's dashboard. Where to set the webhook depends on where
+you got your :setting:`UNISENDER_GO_API_KEY <ANYMAIL_UNISENDER_GO_API_KEY>`:
+
+* If you are using an account-level API key, configure the webhook
+  under Settings > Webhooks (Настройки > Вебхуки).
+* If you are using a project-level API key, configure the webhook
+  under Settings > Projects (Настройки > Проекты).
+
+(If you try to mix account-level and project-level API keys and webhooks,
+webhook signature validation will fail, and you'll get
+:exc:`~anymail.exceptions.AnymailWebhookValidationFailure` errors.)
+
+Enter these settings for the webhook:
+
+*  **Notification Url:**
+
+       :samp:`https://{yoursite.example.com}/anymail/unisender_go/tracking/`
+
+   where *yoursite.example.com* is your Django site.
+
+*  **Status:** set to "Active" if you have already deployed your Django project
+   with Anymail installed. Otherwise set to "Inactive" and update after you deploy.
+
+   (Unisender Go performs a GET request to verify the webhook URL
+   when it is marked active.)
+
+*  **Event format:** "json_post"
+
+   (If your gateway handles decompressing incoming request bodies---e.g., Apache
+   with a mod_deflate *input* filter---you could also use "json_post_compressed."
+   Most web servers do not handle compressed input by default.)
+
+*  **Events:** your choice. Anymail supports any combination of ``sent, delivered,
+   soft_bounced, hard_bounced, opened, clicked, unsubscribed, subscribed, spam``.
+
+   Anymail does not support Unisender Go's ``spam_block`` events (but will ignore
+   them if you accidentally include it).
+
+*  **Number of simultaneous requests:** depends on your web server's
+   capacity
+
+   Most deployments should be able to handle the default 10.
+   But you may need to use a smaller number if your tracking signal
+   receiver uses a lot of resources (or monopolizes your database),
+   or if your web server isn't configured to handle that many
+   simultaneous requests (including requests from your site users).
+
+*  **Use single event:** the default "No" is recommended
+
+   Anymail can process multiple events in a single webhook call.
+   It invokes your signal receiver separately for each event.
+   But all of the events in the call (up to 100 when set to "No")
+   must be handled within 3 seconds total, or Unisender Go will
+   think the request failed and resend it.
+
+   If your tracking signal receiver takes a long time to process
+   each event, you may need to change "Use single event" to "Yes"
+   (one event per webhook call).
+
+*  **Additional information about delivery:** "Yes" is recommended
+
+   (If you set this to "No", your tracking events won't include
+   :attr:`~anymail.signals.AnymailTrackingEvent.mta_response`,
+   :attr:`~anymail.signals.AnymailTrackingEvent.user_agent` or
+   :attr:`~anymail.signals.AnymailTrackingEvent.click_url`.)
+
+Note that Unisender Go does not deliver tracking events for recipient
+addresses that are blocked at send time. You must check the message's
+:attr:`anymail_status.recipients[recipient_email].message_id <anymail.message.AnymailStatus.recipients>`
+immediately after sending to detect rejected recipients.
+
+Unisender Go implements webhook signing on the entire event payload,
+and Anymail verifies this signature using your
+:setting:`UNISENDER_GO_API_KEY <ANYMAIL_UNISENDER_GO_API_KEY>`.
+It is not necessary to use an :setting:`ANYMAIL_WEBHOOK_SECRET`
+with Unisender Go, but if you have set one, you must include
+the *random:random* shared secret in the Notification URL like this:
+
+     :samp:`https://{random}:{random}@{yoursite.example.com}/anymail/unisender_go/tracking/`
+
+In your tracking signal receiver, the event's
+:attr:`~anymail.signals.AnymailTrackingEvent.esp_event` field will be
+the ``"event_data"`` object from a single, raw `"transactional_email_status" event`_.
+For example, you could get the IP address that opened a message using
+``event.esp_event["delivery_info"]["ip"]``.
+
+(Anymail does not handle Unisender Go's "transactional_spam_block" events,
+and will filter these without calling your tracking signal handler.)
+
+.. _"transactional_email_status" event:
+    https://godocs.unisender.ru/web-api-ref#callback-format
+
+
+.. _unisender-go-inbound:
+
+Inbound webhook
+---------------
+
+Unisender Go does not currently offer inbound email.
+
+(If this changes in the future, please open an issue
+so we can add support in Anymail.)
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -14,7 +14,7 @@ authors = [
 description = """\
    Django email backends and webhooks for Amazon SES, Brevo (Sendinblue),
    MailerSend, Mailgun, Mailjet, Mandrill, Postal, Postmark, Resend,
-    SendGrid, and SparkPost\
+    SendGrid, SparkPost and Unisender Go\
    """
 # readme: see tool.hatch.metadata.hooks.custom below
 keywords = [
@@ -25,6 +25,7 @@ keywords = [
    "Postal", "Postmark",
    "Resend",
    "SendGrid", "SendinBlue", "SparkPost",
+    "Unisender Go",
 ]
 classifiers = [
    "Development Status :: 5 - Production/Stable",
@@ -74,6 +75,7 @@ resend = ["svix"]
 sendgrid = []
 sendinblue = []
 sparkpost = []
+unisender-go = []
 postal = [
    # Postal requires cryptography for verifying webhooks.
    # Cryptography's wheels are broken on darwin-arm64 before Python 3.9.
--- a/tests/test_unisender_go_backend.py
+++ b/tests/test_unisender_go_backend.py
@@ -0,0 +1,895 @@
+import json
+from base64 import b64encode
+from datetime import date, datetime
+from decimal import Decimal
+from email.mime.base import MIMEBase
+from email.mime.image import MIMEImage
+from unittest.mock import patch
+
+from django.core import mail
+from django.test import SimpleTestCase, override_settings, tag
+from django.utils.timezone import (
+    get_fixed_timezone,
+    override as override_current_timezone,
+)
+
+from anymail.exceptions import (
+    AnymailAPIError,
+    AnymailConfigurationError,
+    AnymailRecipientsRefused,
+    AnymailSerializationError,
+    AnymailUnsupportedFeature,
+)
+from anymail.message import AnymailMessage, attach_inline_image_file
+
+from .mock_requests_backend import (
+    RequestsBackendMockAPITestCase,
+    SessionSharingTestCases,
+)
+from .utils import (
+    SAMPLE_IMAGE_FILENAME,
+    AnymailTestMixin,
+    sample_image_content,
+    sample_image_path,
+)
+
+
+@tag("unisender_go")
+@override_settings(
+    EMAIL_BACKEND="anymail.backends.unisender_go.EmailBackend",
+    ANYMAIL={
+        "UNISENDER_GO_API_KEY": "test_api_key",
+        "UNISENDER_GO_API_URL": "https://go1.unisender.ru/ru/transactional/api/v1",
+    },
+)
+class UnisenderGoBackendMockAPITestCase(RequestsBackendMockAPITestCase):
+    DEFAULT_RAW_RESPONSE = json.dumps(
+        {
+            "status": "success",
+            "job_id": "1rctPx-00021H-CcC4",
+            "emails": ["to@example.com"],
+        }
+    ).encode("utf-8")
+    DEFAULT_STATUS_CODE = 200
+    DEFAULT_CONTENT_TYPE = "application/json"
+
+    def setUp(self):
+        super().setUp()
+
+        # Patch uuid4 to generate predictable message_ids for testing
+        patch_uuid4 = patch(
+            "anymail.backends.unisender_go.uuid.uuid4",
+            side_effect=[f"mocked-uuid-{n:d}" for n in range(1, 10)],
+        )
+        patch_uuid4.start()
+        self.addCleanup(patch_uuid4.stop)
+
+        # Simple message useful for many tests
+        self.message = AnymailMessage(
+            "Subject", "Text Body", "from@example.com", ["to@example.com"]
+        )
+
+    def set_mock_response(
+        self, success_emails=None, failed_emails=None, job_id=None, **kwargs
+    ):
+        """
+        Pass success_emails and/or failure_emails to generate an appropriate
+        API response for those specific emails. Otherwise, arguments are as
+        for super call.
+        :param success_emails {list[str]}: addr-specs of emails that were delivered
+        :param failure_emails {dict[str,str]}: mapping of addr-spec -> failure reason
+        :param job_id {str}: optional specific job_id for response
+        """
+        if success_emails or failed_emails:
+            assert "raw" not in kwargs
+            assert "json_response" not in kwargs
+            assert kwargs.get("status_code", 200) == 200
+            kwargs["status_code"] = 200
+            kwargs["json_data"] = {
+                "status": "success",
+                "job_id": job_id or "1rctPx-00021H-CcC4",
+                "emails": success_emails or [],
+            }
+            if failed_emails:
+                kwargs["json_data"]["failed_emails"] = failed_emails
+
+        return super().set_mock_response(**kwargs)
+
+
+@tag("unisender_go")
+class UnisenderGoBackendStandardEmailTests(UnisenderGoBackendMockAPITestCase):
+    """Test backend support for Django standard email features"""
+
+    def test_send_mail(self):
+        """Test basic API for simple send"""
+        mail.send_mail(
+            "Subject here",
+            "Here is the message.",
+            "from@sender.example.com",
+            ["to@example.com"],
+            fail_silently=False,
+        )
+        self.assert_esp_called(
+            "https://go1.unisender.ru/ru/transactional/api/v1/email/send.json"
+        )
+        http_headers = self.get_api_call_headers()
+        self.assertEqual(http_headers["X-API-KEY"], "test_api_key")
+        self.assertEqual(http_headers["Accept"], "application/json")
+        self.assertEqual(http_headers["Content-Type"], "application/json")
+
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["subject"], "Subject here")
+        self.assertEqual(data["message"]["body"], {"plaintext": "Here is the message."})
+        self.assertEqual(data["message"]["from_email"], "from@sender.example.com")
+        self.assertEqual(
+            data["message"]["recipients"],
+            [
+                {
+                    "email": "to@example.com",
+                    # make sure the backend assigned the message_id
+                    # for event tracking and notification
+                    "metadata": {"anymail_id": "mocked-uuid-1"},
+                }
+            ],
+        )
+
+    def test_name_addr(self):
+        """Make sure RFC2822 name-addr format (with display-name) is allowed
+
+        (Test both sender and recipient addresses)
+        """
+        msg = mail.EmailMessage(
+            "Subject",
+            "Message",
+            "From Name <from@example.com>",
+            ["Recipient #1 <to1@example.com>", "to2@example.com"],
+            cc=["Carbon Copy <cc1@example.com>", "cc2@example.com"],
+            bcc=["Blind Copy <bcc1@example.com>", "bcc2@example.com"],
+        )
+        msg.send()
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["from_email"], "from@example.com")
+        self.assertEqual(data["message"]["from_name"], "From Name")
+
+        recipients = data["message"]["recipients"]
+        self.assertEqual(len(recipients), 6)
+        self.assertEqual(recipients[0]["email"], "to1@example.com")
+        self.assertEqual(recipients[0]["substitutions"]["to_name"], "Recipient #1")
+        self.assertEqual(recipients[1]["email"], "to2@example.com")
+        self.assertNotIn("substitutions", recipients[1])  # to_name not needed
+        self.assertEqual(recipients[2]["email"], "cc1@example.com")
+        self.assertEqual(recipients[2]["substitutions"]["to_name"], "Carbon Copy")
+        self.assertEqual(recipients[3]["email"], "cc2@example.com")
+        self.assertNotIn("substitutions", recipients[3])  # to_name not needed
+        self.assertEqual(recipients[4]["email"], "bcc1@example.com")
+        self.assertEqual(recipients[4]["substitutions"]["to_name"], "Blind Copy")
+        self.assertEqual(recipients[5]["email"], "bcc2@example.com")
+        self.assertNotIn("substitutions", recipients[5])  # to_name not needed
+
+        # This also covers Unisender Go's special handling for cc/bcc
+        headers = data["message"]["headers"]
+        self.assertEqual(
+            headers["to"], "Recipient #1 <to1@example.com>, to2@example.com"
+        )
+        self.assertEqual(
+            headers["cc"], "Carbon Copy <cc1@example.com>, cc2@example.com"
+        )
+        self.assertNotIn("bcc", headers)
+
+    def test_display_names_with_special_chars(self):
+        # Verify workaround for Unisender Go bug parsing to/cc headers
+        # with display names containing commas, angle brackets, or at sign
+        self.message.to = [
+            '"With, Comma" <to1@example.com>',
+            '"angle <brackets>" <to2@example.com>',
+            '"(without) special / chars" <to3@example.com>',
+        ]
+        self.message.cc = [
+            '"Someone @example.com" <cc1@example.com>',
+            '"[without] special & chars" <cc2@example.com>',
+        ]
+        self.message.send()
+        data = self.get_api_call_json()
+        headers = data["message"]["headers"]
+        # display-name with , < > @ converted to RFC 2047 encoded word;
+        # not necessary for display names with other special characters
+        self.assertEqual(
+            headers["to"],
+            "=?utf-8?q?With=2C_Comma?= <to1@example.com>, "
+            "=?utf-8?q?angle_=3Cbrackets=3E?= <to2@example.com>, "
+            '"(without) special / chars" <to3@example.com>',
+        )
+        self.assertEqual(
+            headers["cc"],
+            "=?utf-8?q?Someone_=40example=2Ecom?= <cc1@example.com>, "
+            '"[without] special & chars" <cc2@example.com>',
+        )
+
+    def test_html_message(self):
+        text_content = "This is an important message."
+        html_content = "<p>This is an <strong>important</strong> message.</p>"
+        email = mail.EmailMultiAlternatives(
+            "Subject", text_content, "from@example.com", ["to@example.com"]
+        )
+        email.attach_alternative(html_content, "text/html")
+        email.send()
+        data = self.get_api_call_json()
+        self.assertEqual(
+            data["message"]["body"], {"plaintext": text_content, "html": html_content}
+        )
+        # Don't accidentally send the html part as an attachment:
+        self.assertNotIn("attachments", data["message"])
+
+    def test_html_only_message(self):
+        html_content = "<p>This is an <strong>important</strong> message.</p>"
+        email = mail.EmailMessage(
+            "Subject", html_content, "from@example.com", ["to@example.com"]
+        )
+        email.content_subtype = "html"  # Main content is now text/html
+        email.send()
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["body"], {"html": html_content})
+
+    def test_amp_html_alternative(self):
+        # Unisender Go *does* support text/x-amp-html alongside text/html
+        self.message.attach_alternative("<p>HTML</p>", "text/html")
+        self.message.attach_alternative("<p>And AMP HTML</p>", "text/x-amp-html")
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["body"]["html"], "<p>HTML</p>")
+        self.assertEqual(data["message"]["body"]["amp"], "<p>And AMP HTML</p>")
+
+    def test_extra_headers(self):
+        self.message.extra_headers = {
+            "X-Custom": "string",
+            "X-Num": 123,
+            "Reply-To": "noreply@example.com",
+        }
+        self.message.send()
+        data = self.get_api_call_json()
+        headers = data["message"]["headers"]
+        self.assertEqual(headers["X-Custom"], "string")
+        self.assertEqual(headers["X-Num"], 123)
+
+        # Reply-To must be moved to separate param
+        self.assertNotIn("Reply-To", headers)
+        self.assertEqual(data["message"]["reply_to"], "noreply@example.com")
+        self.assertNotIn("reply_to_name", data["message"])
+
+    def test_extra_headers_serialization_error(self):
+        self.message.extra_headers = {"X-Custom": Decimal(12.5)}
+        with self.assertRaisesMessage(AnymailSerializationError, "Decimal"):
+            self.message.send()
+
+    def test_reply_to(self):
+        # Unisender Go supports only a single reply-to
+        self.message.reply_to = ['"Reply recipient" <reply@example.com']
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["reply_to"], "reply@example.com")
+        self.assertEqual(data["message"]["reply_to_name"], "Reply recipient")
+
+    def test_reply_to_name_workaround(self):
+        # Check workaround for reply-to display-name containing special chars
+        self.message.reply_to = ['"Reply (parens)" <reply@example.com']
+        self.message.send()
+        data = self.get_api_call_json()
+        # Special chars force RFC 2047 encoded word
+        self.assertEqual(
+            data["message"]["reply_to_name"], "=?utf-8?q?Reply_=28parens=29?="
+        )
+
+    def test_attachments(self):
+        text_content = "* Item one\n* Item two\n* Item three"
+        self.message.attach(
+            filename="test.txt", content=text_content, mimetype="text/plain"
+        )
+
+        # Should guess mimetype if not provided...
+        png_content = b"PNG\xb4 pretend this is the contents of a png file"
+        self.message.attach(filename="test.png", content=png_content)
+
+        # Should work with a MIMEBase object (also tests no filename)...
+        pdf_content = b"PDF\xb4 pretend this is valid pdf data"
+        mimeattachment = MIMEBase("application", "pdf")
+        mimeattachment.set_payload(pdf_content)
+        self.message.attach(mimeattachment)
+
+        self.message.send()
+        data = self.get_api_call_json()
+        attachments = data["message"]["attachments"]
+        self.assertEqual(len(attachments), 3)
+
+        self.assertEqual(
+            attachments[0],
+            {
+                "name": "test.txt",
+                "content": b64encode(text_content.encode("utf-8")).decode("ascii"),
+                "type": "text/plain",
+            },
+        )
+        self.assertEqual(
+            attachments[1],
+            {
+                "name": "test.png",
+                "content": b64encode(png_content).decode("ascii"),
+                "type": "image/png",  # (type inferred from filename)
+            },
+        )
+        self.assertEqual(
+            attachments[2],
+            {
+                "name": "",  # no filename -- but param is required
+                "content": b64encode(pdf_content).decode("ascii"),
+                "type": "application/pdf",
+            },
+        )
+
+    def test_embedded_images(self):
+        image_filename = SAMPLE_IMAGE_FILENAME
+        image_path = sample_image_path(image_filename)
+        image_data = sample_image_content(image_filename)
+
+        cid = attach_inline_image_file(self.message, image_path)  # Read from a png file
+        html_content = (
+            '<p>This has an <img src="cid:%s" alt="inline" /> image.</p>' % cid
+        )
+        self.message.attach_alternative(html_content, "text/html")
+
+        self.message.send()
+        data = self.get_api_call_json()
+
+        self.assertEqual(
+            data["message"]["inline_attachments"],
+            [
+                {
+                    "name": cid,
+                    "content": b64encode(image_data).decode("ascii"),
+                    "type": "image/png",  # (type inferred from filename)
+                }
+            ],
+        )
+
+    def test_attached_images(self):
+        image_filename = SAMPLE_IMAGE_FILENAME
+        image_path = sample_image_path(image_filename)
+        image_data = sample_image_content(image_filename)
+
+        # option 1: attach as a file
+        self.message.attach_file(image_path)
+
+        # option 2: construct the MIMEImage and attach it directly
+        image = MIMEImage(image_data)
+        self.message.attach(image)
+
+        self.message.send()
+
+        image_data_b64 = b64encode(image_data).decode("ascii")
+        data = self.get_api_call_json()
+        self.assertEqual(
+            data["message"]["attachments"][0],
+            {
+                "name": image_filename,  # the named one
+                "content": image_data_b64,
+                "type": "image/png",
+            },
+        )
+        self.assertEqual(
+            data["message"]["attachments"][1],
+            {
+                "name": "",  # the unnamed one
+                "content": image_data_b64,
+                "type": "image/png",
+            },
+        )
+
+    def test_multiple_html_alternatives(self):
+        # Multiple alternatives not allowed
+        self.message.attach_alternative("<p>First html is OK</p>", "text/html")
+        self.message.attach_alternative("<p>But not second html</p>", "text/html")
+        with self.assertRaises(AnymailUnsupportedFeature):
+            self.message.send()
+
+    def test_non_html_alternative(self):
+        # Only html alternatives allowed
+        self.message.attach_alternative("{'not': 'allowed'}", "application/json")
+        with self.assertRaises(AnymailUnsupportedFeature):
+            self.message.send()
+
+    def test_api_failure(self):
+        self.set_mock_response(status_code=400)
+        with self.assertRaisesMessage(AnymailAPIError, "Unisender Go API response 400"):
+            mail.send_mail("Subject", "Body", "from@example.com", ["to@example.com"])
+
+        # Make sure fail_silently is respected
+        self.set_mock_response(status_code=400)
+        sent = mail.send_mail(
+            "Subject",
+            "Body",
+            "from@example.com",
+            ["to@example.com"],
+            fail_silently=True,
+        )
+        self.assertEqual(sent, 0)
+
+    def test_api_error_includes_details(self):
+        """AnymailAPIError should include ESP's error message"""
+        self.set_mock_response(
+            status_code=400,
+            json_data=[
+                {
+                    "status": "error",
+                    "message": "Helpful explanation from Unisender Go",
+                    "code": 999,
+                },
+            ],
+        )
+        with self.assertRaisesMessage(
+            AnymailAPIError, "Helpful explanation from Unisender Go"
+        ):
+            self.message.send()
+
+
+@tag("unisender_go")
+class UnisenderGoBackendAnymailFeatureTests(UnisenderGoBackendMockAPITestCase):
+    """Test backend support for Anymail added features"""
+
+    def test_envelope_sender(self):
+        # Unisender Go does not have a way to change envelope sender.
+        self.message.envelope_sender = "anything@bounces.example.com"
+        with self.assertRaisesMessage(AnymailUnsupportedFeature, "envelope_sender"):
+            self.message.send()
+
+    def test_metadata(self):
+        self.message.metadata = {"user_id": "12345", "items": 6, "float": 98.6}
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertEqual(
+            data["message"]["global_metadata"],
+            {
+                "user_id": "12345",
+                "items": 6,
+                "float": 98.6,
+            },
+        )
+
+    def test_send_at(self):
+        utc_plus_6 = get_fixed_timezone(6 * 60)
+        utc_minus_8 = get_fixed_timezone(-8 * 60)
+
+        with override_current_timezone(utc_plus_6):
+            # Timezone-naive datetime assumed to be Django current_timezone
+            self.message.send_at = datetime(2022, 10, 11, 12, 13, 14, 567)
+            self.message.send()
+            data = self.get_api_call_json()
+            self.assertEqual(
+                data["message"]["options"]["send_at"], "2022-10-11 06:13:14"
+            )  # 12:13 UTC+6 == 06:13 UTC
+
+            # Timezone-aware datetime converted to UTC:
+            self.message.send_at = datetime(2016, 3, 4, 5, 6, 7, tzinfo=utc_minus_8)
+            self.message.send()
+            data = self.get_api_call_json()
+            self.assertEqual(
+                data["message"]["options"]["send_at"], "2016-03-04 13:06:07"
+            )  # 05:06 UTC-8 == 13:06 UTC
+
+            # Date-only treated as midnight in current timezone
+            self.message.send_at = date(2022, 10, 22)
+            self.message.send()
+            data = self.get_api_call_json()
+            self.assertEqual(
+                data["message"]["options"]["send_at"], "2022-10-21 18:00:00"
+            )  # 00:00 UTC+6 == 18:00-1d UTC
+
+            # POSIX timestamp
+            self.message.send_at = 1651820889  # 2022-05-06 07:08:09 UTC
+            self.message.send()
+            data = self.get_api_call_json()
+            self.assertEqual(
+                data["message"]["options"]["send_at"], "2022-05-06 07:08:09"
+            )
+
+            # String passed unchanged (this is *not* portable between ESPs)
+            self.message.send_at = "2013-11-12 01:02:03"
+            self.message.send()
+            data = self.get_api_call_json()
+            self.assertEqual(
+                data["message"]["options"]["send_at"], "2013-11-12 01:02:03"
+            )
+
+    def test_tags(self):
+        self.message.tags = ["receipt", "repeat-user"]
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertCountEqual(data["message"]["tags"], ["receipt", "repeat-user"])
+
+    def test_tracking(self):
+        # Test one way...
+        self.message.track_clicks = False
+        self.message.track_opens = True
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["track_links"], 0)
+        self.assertEqual(data["message"]["track_read"], 1)
+
+        # ...and the opposite way
+        self.message.track_clicks = True
+        self.message.track_opens = False
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertEqual(data["message"]["track_links"], 1)
+        self.assertEqual(data["message"]["track_read"], 0)
+
+    def test_template_id(self):
+        self.message.template_id = "5997fcf6-2b9f-484d-acd5-7e9a99f0dc1f"
+        self.message.send()
+        data = self.get_api_call_json()
+        self.assertEqual(
+            data["message"]["template_id"], "5997fcf6-2b9f-484d-acd5-7e9a99f0dc1f"
+        )
+
+    def test_merge_data(self):
+        self.message.from_email = "from@example.com"
+        self.message.to = [
+            "alice@example.com",
+            "Bob <bob@example.com>",
+            "celia@example.com",
+        ]
+        self.message.merge_data = {
+            "alice@example.com": {"name": "Alice", "group": "Developers"},
+            "bob@example.com": {"name": "Robert"},  # and leave group undefined
+            # and no data for celia@example.com
+        }
+        self.message.merge_global_data = {
+            "group": "Users",
+            "site": "ExampleCo",
+        }
+        self.message.send()
+
+        data = self.get_api_call_json()
+        recipients = data["message"]["recipients"]
+        self.assertEqual(recipients[0]["email"], "alice@example.com")
+        self.assertEqual(
+            recipients[0]["substitutions"], {"name": "Alice", "group": "Developers"}
+        )
+        self.assertEqual(recipients[1]["email"], "bob@example.com")
+        self.assertEqual(
+            # Make sure email display name (as "to_name") is combined with merge_data
+            recipients[1]["substitutions"],
+            {"name": "Robert", "to_name": "Bob"},
+        )
+        self.assertEqual(recipients[2]["email"], "celia@example.com")
+        self.assertNotIn("substitutions", recipients[2])
+        self.assertEqual(
+            data["message"]["global_substitutions"],
+            {"group": "Users", "site": "ExampleCo"},
+        )
+
+        # For batch send, must not include common "to" header
+        headers = data["message"].get("headers", {})
+        self.assertNotIn("to", headers)
+        self.assertNotIn("cc", headers)
+
+    def test_merge_metadata(self):
+        self.message.to = ["alice@example.com", "Bob <bob@example.com>"]
+        self.message.merge_metadata = {
+            "alice@example.com": {"order_id": 123},
+            "bob@example.com": {"order_id": 678, "tier": "premium"},
+        }
+        self.message.send()
+        data = self.get_api_call_json()
+        recipients = data["message"]["recipients"]
+        # anymail_id added to other recipient metadata
+        self.assertEqual(
+            recipients[0]["metadata"],
+            {
+                "anymail_id": "mocked-uuid-1",
+                "order_id": 123,
+            },
+        )
+        self.assertEqual(
+            recipients[1]["metadata"],
+            {
+                "anymail_id": "mocked-uuid-2",
+                "order_id": 678,
+                "tier": "premium",
+            },
+        )
+
+        # For batch send, must not include common "to" header
+        headers = data["message"].get("headers", {})
+        self.assertNotIn("to", headers)
+        self.assertNotIn("cc", headers)
+
+    def test_cc_unsupported_with_batch_send(self):
+        self.message.merge_data = {}
+        self.message.cc = ["cc@example.com"]
+        with self.assertRaisesMessage(
+            AnymailUnsupportedFeature,
+            "cc with batch send (merge_data or merge_metadata)",
+        ):
+            self.message.send()
+
+    @override_settings(ANYMAIL_IGNORE_UNSUPPORTED_FEATURES=True)
+    def test_ignore_unsupported_cc_with_batch_send(self):
+        self.message.merge_data = {}
+        self.message.cc = ["cc@example.com"]
+        self.message.bcc = ["bcc@example.com"]
+        self.message.send()
+        self.assertEqual(self.message.anymail_status.status, {"queued"})
+        data = self.get_api_call_json()
+        # Unisender Go prohibits "cc" header without "to" header,
+        # and we can't include a "to" header for batch send,
+        # so make sure we've removed the "cc" header when ignoring unsupported cc
+        headers = data["message"].get("headers", {})
+        self.assertNotIn("cc", headers)
+        self.assertNotIn("to", headers)
+
+    @override_settings(ANYMAIL_UNISENDER_GO_GENERATE_MESSAGE_ID=False)
+    def test_default_omits_options(self):
+        """Make sure by default we don't send any ESP-specific options.
+
+        Options not specified by the caller should be omitted entirely from
+        the API call (*not* sent as False or empty). This ensures
+        that your ESP account settings apply by default.
+        """
+        self.message.send()
+        message_data = self.get_api_call_json()["message"]
+        self.assertNotIn("attachments", message_data)
+        self.assertNotIn("from_name", message_data)
+        self.assertNotIn("global_substitutions", message_data)
+        self.assertNotIn("global_metadata", message_data)
+        self.assertNotIn("inline_attachments", message_data)
+        self.assertNotIn("options", message_data)
+        self.assertNotIn("reply_to", message_data)
+        self.assertNotIn("reply_to_name", message_data)
+        self.assertNotIn("tags", message_data)
+        self.assertNotIn("template_id", message_data)
+        self.assertNotIn("track_links", message_data)
+        self.assertNotIn("track_read", message_data)
+
+        for recipient_data in message_data["recipients"]:
+            self.assertNotIn("metadata", recipient_data)
+            self.assertNotIn("substitutions", recipient_data)
+
+    def test_esp_extra(self):
+        self.message.send_at = "2022-02-22 22:22:22"
+        self.message.esp_extra = {
+            "global_language": "en",
+            "skip_unsubscribe": 1,
+            "template_engine": "velocity",
+            "options": {
+                "unsubscribe_url": "https://example.com/unsubscribe?id={{user_id}}",
+                "smtp_pool_id": "custom-smtp-pool",
+            },
+        }
+        self.message.send()
+        data = self.get_api_call_json()
+        # merged from esp_extra:
+        self.assertEqual(data["message"]["global_language"], "en")
+        self.assertEqual(data["message"]["skip_unsubscribe"], 1)
+        self.assertEqual(data["message"]["template_engine"], "velocity")
+        self.assertEqual(
+            data["message"]["options"],
+            {  # deep merge
+                "send_at": "2022-02-22 22:22:22",
+                "unsubscribe_url": "https://example.com/unsubscribe?id={{user_id}}",
+                "smtp_pool_id": "custom-smtp-pool",
+            },
+        )
+
+    # noinspection PyUnresolvedReferences
+    def test_send_attaches_anymail_status(self):
+        """The anymail_status should be attached to the message when it is sent"""
+        msg = mail.EmailMessage(
+            "Subject",
+            "Message",
+            "from@example.com",
+            ["to@example.com"],
+        )
+        sent = msg.send()
+        self.assertEqual(sent, 1)
+        self.assertEqual(msg.anymail_status.status, {"queued"})
+        self.assertEqual(msg.anymail_status.message_id, "mocked-uuid-1")
+        self.assertEqual(
+            msg.anymail_status.recipients["to@example.com"].status, "queued"
+        )
+        self.assertEqual(
+            msg.anymail_status.recipients["to@example.com"].message_id, "mocked-uuid-1"
+        )
+        self.assertEqual(
+            msg.anymail_status.esp_response.content, self.DEFAULT_RAW_RESPONSE
+        )
+
+    def test_batch_recipients_get_unique_message_ids(self):
+        """In a batch send, each recipient should get a distinct message_id"""
+        # Unisender Go *always* uses batch send; no need to force by setting merge_data.
+        self.set_mock_response(success_emails=["to1@example.com", "to2@example.com"])
+        msg = mail.EmailMessage(
+            "Subject",
+            "Message",
+            "from@example.com",
+            ["to1@example.com", "Someone Else <to2@example.com>"],
+        )
+        msg.send()
+        self.assertEqual(
+            msg.anymail_status.message_id, {"mocked-uuid-1", "mocked-uuid-2"}
+        )
+        self.assertEqual(
+            msg.anymail_status.recipients["to1@example.com"].message_id, "mocked-uuid-1"
+        )
+        self.assertEqual(
+            msg.anymail_status.recipients["to2@example.com"].message_id, "mocked-uuid-2"
+        )
+
+    def test_rejected_recipient_status(self):
+        self.message.to = [
+            "duplicate@example.com",
+            "Again <duplicate@example.com>",
+            "Duplicate@example.com",  # addresses are case-insensitive
+            "bounce@example.com",
+            "mailbox-full@example.com",
+            "webmaster@localhost",
+            "spam-report@example.com",
+        ]
+        self.set_mock_response(
+            # Note "duplicate" email will appear in both success and failed lists
+            # (because Unisender Go sends the first one, fails remaining duplicates)
+            success_emails=["duplicate@example.com"],
+            failed_emails={
+                "duplicate@example.com": "duplicate",
+                "Duplicate@example.com": "duplicate",
+                "bounce@example.com": "permanent_unavailable",
+                "mailbox-full@example.com": "temporary_unavailable",
+                "webmaster@localhost": "invalid",
+                "spam-report@example.com": "unsubscribed",
+            },
+        )
+        self.message.send()
+        recipient_status = self.message.anymail_status.recipients
+        self.assertEqual(recipient_status["duplicate@example.com"].status, "queued")
+        self.assertEqual(
+            # duplicate uses _first_ message_id (because first instance will be sent)
+            recipient_status["duplicate@example.com"].message_id,
+            "mocked-uuid-1",
+        )
+        self.assertEqual(recipient_status["bounce@example.com"].status, "rejected")
+        self.assertIsNone(recipient_status["bounce@example.com"].message_id)
+        self.assertEqual(recipient_status["mailbox-full@example.com"].status, "failed")
+        self.assertIsNone(recipient_status["mailbox-full@example.com"].message_id)
+        self.assertEqual(recipient_status["webmaster@localhost"].status, "invalid")
+        self.assertIsNone(recipient_status["webmaster@localhost"].message_id)
+        self.assertEqual(recipient_status["spam-report@example.com"].status, "rejected")
+        self.assertIsNone(recipient_status["spam-report@example.com"].message_id)
+
+    @override_settings(ANYMAIL_UNISENDER_GO_GENERATE_MESSAGE_ID=False)
+    def test_disable_generate_message_id(self):
+        """
+        When not generating per-recipient message_id,
+        use Unisender Go's job_id for all recipients.
+        """
+        self.set_mock_response(
+            success_emails=["to1@example.com", "to2@example.com"],
+            job_id="123456-000HHH-CcCc",
+        )
+        self.message.to = ["to1@example.com", "to2@example.com"]
+        self.message.send()
+        self.assertEqual(self.message.anymail_status.message_id, "123456-000HHH-CcCc")
+        recipient_status = self.message.anymail_status.recipients
+        self.assertEqual(
+            recipient_status["to1@example.com"].message_id, "123456-000HHH-CcCc"
+        )
+        self.assertEqual(
+            recipient_status["to2@example.com"].message_id, "123456-000HHH-CcCc"
+        )
+
+    # noinspection PyUnresolvedReferences
+    def test_send_failed_anymail_status(self):
+        """If the send fails, anymail_status should contain initial values"""
+        self.set_mock_response(status_code=500)
+        sent = self.message.send(fail_silently=True)
+        self.assertEqual(sent, 0)
+        self.assertIsNone(self.message.anymail_status.status)
+        self.assertIsNone(self.message.anymail_status.message_id)
+        self.assertEqual(self.message.anymail_status.recipients, {})
+        self.assertIsNone(self.message.anymail_status.esp_response)
+
+    def test_json_serialization_errors(self):
+        """Try to provide more information about non-json-serializable data"""
+        self.message.metadata = {"total": Decimal("19.99")}
+        with self.assertRaises(AnymailSerializationError) as cm:
+            self.message.send()
+        err = cm.exception
+        self.assertIsInstance(err, TypeError)  # compatibility with json.dumps
+        # our added context:
+        self.assertIn("Don't know how to send this data to Unisender Go", str(err))
+        # original message:
+        self.assertRegex(str(err), r"Decimal.*is not JSON serializable")
+
+
+@tag("unisender_go")
+class UnisenderGoBackendRecipientsRefusedTests(UnisenderGoBackendMockAPITestCase):
+    """
+    Should raise AnymailRecipientsRefused when *all* recipients are rejected or invalid
+    """
+
+    def test_recipients_refused(self):
+        self.message.to = ["invalid@localhost", "reject@example.com"]
+        self.set_mock_response(
+            failed_emails={
+                "invalid@localhost": "invalid",
+                "reject@example.com": "permanent_unavailable",
+            }
+        )
+        with self.assertRaises(AnymailRecipientsRefused):
+            self.message.send()
+
+    def test_fail_silently(self):
+        self.message.to = ["invalid@localhost", "reject@example.com"]
+        self.set_mock_response(
+            failed_emails={
+                "invalid@localhost": "invalid",
+                "reject@example.com": "permanent_unavailable",
+            }
+        )
+        sent = self.message.send(fail_silently=True)
+        self.assertEqual(sent, 0)
+
+    def test_mixed_response(self):
+        """If *any* recipients are valid or queued, no exception is raised"""
+        self.message.to = [
+            "invalid@localhost",
+            "valid@example.com",
+            "reject@example.com",
+            "also.valid@example.com",
+        ]
+        self.set_mock_response(
+            success_emails=["valid@example.com", "also.valid@example.com"],
+            failed_emails={
+                "invalid@localhost": "invalid",
+                "reject@example.com": "permanent_unavailable",
+            },
+        )
+        sent = self.message.send()
+        # one message sent, successfully, to 2 of 4 recipients:
+        self.assertEqual(sent, 1)
+        status = self.message.anymail_status
+        self.assertEqual(status.recipients["invalid@localhost"].status, "invalid")
+        self.assertEqual(status.recipients["valid@example.com"].status, "queued")
+        self.assertEqual(status.recipients["reject@example.com"].status, "rejected")
+        self.assertEqual(status.recipients["also.valid@example.com"].status, "queued")
+
+    @override_settings(ANYMAIL_IGNORE_RECIPIENT_STATUS=True)
+    def test_settings_override(self):
+        """No exception with ignore setting"""
+        self.message.to = ["invalid@localhost", "reject@example.com"]
+        self.set_mock_response(
+            failed_emails={
+                "invalid@localhost": "invalid",
+                "reject@example.com": "permanent_unavailable",
+            }
+        )
+        sent = self.message.send()
+        self.assertEqual(sent, 1)  # refused message is included in sent count
+
+
+@tag("unisender_go")
+class UnisenderGoBackendSessionSharingTestCase(
+    SessionSharingTestCases, UnisenderGoBackendMockAPITestCase
+):
+    """Requests session sharing tests"""
+
+    pass  # tests are defined in SessionSharingTestCases
+
+
+@tag("unisender_go")
+@override_settings(EMAIL_BACKEND="anymail.backends.unisender_go.EmailBackend")
+class UnisenderGoBackendImproperlyConfiguredTests(AnymailTestMixin, SimpleTestCase):
+    """Test ESP backend without required settings in place"""
+
+    def test_missing_auth(self):
+        with self.assertRaisesRegex(
+            AnymailConfigurationError, r"\bUNISENDER_GO_API_KEY\b"
+        ):
+            mail.send_mail("Subject", "Message", "from@example.com", ["to@example.com"])
--- a/tests/test_unisender_go_integration.py
+++ b/tests/test_unisender_go_integration.py
@@ -0,0 +1,172 @@
+import os
+import unittest
+from datetime import datetime, timedelta
+from email.headerregistry import Address
+
+from django.test import SimpleTestCase, override_settings, tag
+
+from anymail.exceptions import AnymailAPIError
+from anymail.message import AnymailMessage
+
+from .utils import AnymailTestMixin
+
+ANYMAIL_TEST_UNISENDER_GO_API_KEY = os.getenv("ANYMAIL_TEST_UNISENDER_GO_API_KEY")
+ANYMAIL_TEST_UNISENDER_GO_API_URL = os.getenv("ANYMAIL_TEST_UNISENDER_GO_API_URL")
+ANYMAIL_TEST_UNISENDER_GO_DOMAIN = os.getenv("ANYMAIL_TEST_UNISENDER_GO_DOMAIN")
+ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID = os.getenv(
+    "ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID"
+)
+
+
+@tag("unisender_go", "live")
+@unittest.skipUnless(
+    ANYMAIL_TEST_UNISENDER_GO_API_KEY
+    and ANYMAIL_TEST_UNISENDER_GO_API_URL
+    and ANYMAIL_TEST_UNISENDER_GO_DOMAIN,
+    "Set ANYMAIL_TEST_UNISENDER_GO_API_KEY, ANYMAIL_TEST_UNISENDER_GO_API_URL"
+    " and ANYMAIL_TEST_UNISENDER_GO_DOMAIN environment variables to run Unisender Go"
+    " integration tests",
+)
+@override_settings(
+    ANYMAIL_UNISENDER_GO_API_KEY=ANYMAIL_TEST_UNISENDER_GO_API_KEY,
+    ANYMAIL_UNISENDER_GO_API_URL=ANYMAIL_TEST_UNISENDER_GO_API_URL,
+    EMAIL_BACKEND="anymail.backends.unisender_go.EmailBackend",
+)
+class UnisenderGoBackendIntegrationTests(AnymailTestMixin, SimpleTestCase):
+    """
+    Unisender Go API integration tests
+
+    These tests run against the **live** Unisender Go API, using the
+    environment variable `ANYMAIL_TEST_UNISENDER_GO_API_KEY` as the API key,
+    `ANYMAIL_UNISENDER_GO_API_URL` as the API URL where that key was issued,
+    and `ANYMAIL_TEST_UNISENDER_GO_DOMAIN` to construct the sender addresses.
+    If any of those variables are not set, these tests won't run.
+
+    To run the template test, also set ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID
+    to a valid template in your account.
+
+    The tests send actual email to a sink address at anymail.dev.
+    """
+
+    def setUp(self):
+        super().setUp()
+        self.from_email = f"from@{ANYMAIL_TEST_UNISENDER_GO_DOMAIN}"
+        self.message = AnymailMessage(
+            "Anymail Unisender Go integration test",
+            "Text content",
+            self.from_email,
+            ["test+to1@anymail.dev"],
+        )
+        self.message.attach_alternative("<p>HTML content</p>", "text/html")
+
+    def test_simple_send(self):
+        # Example of getting the Unisender Go send status and message id from the message
+        sent_count = self.message.send()
+        self.assertEqual(sent_count, 1)
+
+        anymail_status = self.message.anymail_status
+        sent_status = anymail_status.recipients["test+to1@anymail.dev"].status
+        message_id = anymail_status.recipients["test+to1@anymail.dev"].message_id
+
+        self.assertEqual(sent_status, "queued")  # Unisender Go always queues
+        self.assertRegex(message_id, r".+")
+        # set of all recipient statuses:
+        self.assertEqual(anymail_status.status, {sent_status})
+        self.assertEqual(anymail_status.message_id, message_id)
+
+    def test_all_options(self):
+        send_at = datetime.now() + timedelta(minutes=2)
+        message = AnymailMessage(
+            subject="Anymail Unisender Go all-options integration test",
+            body="This is the text body",
+            from_email=str(
+                Address(display_name="Test From, with comma", addr_spec=self.from_email)
+            ),
+            to=["test+to1@anymail.dev", '"Recipient 2, OK?" <test+to2@anymail.dev>'],
+            cc=["test+cc1@anymail.dev", '"Copy 2, OK?" <test+cc2@anymail.dev>'],
+            bcc=[
+                f"test+bcc1@{ANYMAIL_TEST_UNISENDER_GO_DOMAIN}",
+                f'"BCC 2, OK?" <bcc2@{ANYMAIL_TEST_UNISENDER_GO_DOMAIN}>',
+            ],
+            # Unisender Go only supports a single reply-to:
+            reply_to=['"Reply, with comma (and parens)" <reply@example.com>'],
+            headers={"X-Anymail-Test": "value", "X-Anymail-Count": 3},
+            metadata={"meta1": "simple string", "meta2": 2},
+            send_at=send_at,
+            tags=["tag 1", "tag 2"],
+            track_opens=False,
+            track_clicks=False,
+            esp_extra={
+                "global_language": "en",
+                "options": {"unsubscribe_url": "https://example.com/unsubscribe?id=1"},
+            },
+        )
+        message.attach_alternative("<p>HTML content</p>", "text/html")
+        message.attach_alternative("<p>AMP HTML content</p>", "text/x-amp-html")
+
+        message.attach("attachment1.txt", "Here is some\ntext for you", "text/plain")
+        message.attach("attachment2.csv", "ID,Name\n1,Amy Lina", "text/csv")
+
+        message.send()
+        self.assertEqual(message.anymail_status.status, {"queued"})
+        recipient_status = message.anymail_status.recipients
+        self.assertEqual(recipient_status["test+to1@anymail.dev"].status, "queued")
+        self.assertEqual(recipient_status["test+to2@anymail.dev"].status, "queued")
+        self.assertRegex(recipient_status["test+to1@anymail.dev"].message_id, r".+")
+        self.assertRegex(recipient_status["test+to2@anymail.dev"].message_id, r".+")
+        # Anymail generates unique message_id for each recipient:
+        self.assertNotEqual(
+            recipient_status["test+to1@anymail.dev"].message_id,
+            recipient_status["test+to2@anymail.dev"].message_id,
+        )
+
+    @unittest.skipUnless(
+        ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID,
+        "Set ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID to run the"
+        " Unisender Go template integration test",
+    )
+    def test_template(self):
+        """
+        To run this test, create a template in your account containing
+        "{{order_id}}" and "{{ship_date}}" substitutions, and set
+        ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID to the template's id.
+        """
+        message = AnymailMessage(
+            # This is an actual template in the Anymail test account:
+            template_id=ANYMAIL_TEST_UNISENDER_GO_TEMPLATE_ID,
+            to=["Recipient 1 <test+to1@anymail.dev>", "test+to2@anymail.dev"],
+            reply_to=["Do not reply <reply@example.dev>"],
+            tags=["using-template"],
+            merge_data={
+                "test+to1@anymail.dev": {"order_id": "12345"},
+                "test+to2@anymail.dev": {"order_id": "23456"},
+            },
+            merge_global_data={"ship_date": "yesterday"},
+            metadata={"customer-id": "unknown", "meta2": 2},
+            merge_metadata={
+                "test+to1@anymail.dev": {"customer-id": "ZXK9123"},
+                "test+to2@anymail.dev": {"customer-id": "ZZT4192"},
+            },
+        )
+        message.from_email = None  # use template sender
+        message.attach("attachment1.txt", "Here is some\ntext", "text/plain")
+
+        message.send()
+        # Unisender Go always queues:
+        self.assertEqual(message.anymail_status.status, {"queued"})
+        recipient_status = message.anymail_status.recipients
+        self.assertEqual(recipient_status["test+to1@anymail.dev"].status, "queued")
+        self.assertEqual(recipient_status["test+to2@anymail.dev"].status, "queued")
+        self.assertRegex(recipient_status["test+to1@anymail.dev"].message_id, r".+")
+        self.assertRegex(recipient_status["test+to2@anymail.dev"].message_id, r".+")
+        # Anymail generates unique message_id for each recipient:
+        self.assertNotEqual(
+            recipient_status["test+to1@anymail.dev"].message_id,
+            recipient_status["test+to2@anymail.dev"].message_id,
+        )
+
+    @override_settings(ANYMAIL_UNISENDER_GO_API_KEY="Hey, that's not an API key!")
+    def test_invalid_api_key(self):
+        # Make sure the exception message includes Unisender Go's response:
+        with self.assertRaisesMessage(AnymailAPIError, "Can not decode key"):
+            self.message.send()
--- a/tests/test_unisender_go_payload.py
+++ b/tests/test_unisender_go_payload.py
@@ -0,0 +1,299 @@
+from __future__ import annotations
+
+from email.headerregistry import Address
+
+from django.test import SimpleTestCase, override_settings, tag
+from requests.structures import CaseInsensitiveDict
+
+from anymail.backends.unisender_go import EmailBackend, UnisenderGoPayload
+from anymail.message import AnymailMessage
+
+TEMPLATE_ID = "template_id"
+FROM_EMAIL = "sender@test.test"
+FROM_NAME = "test name"
+TO_EMAIL = "receiver@test.test"
+TO_NAME = "receiver"
+OTHER_TO_EMAIL = "receiver1@test.test"
+OTHER_TO_NAME = "receiver1"
+SUBJECT = "subject"
+GLOBAL_DATA = {"arg": "arg"}
+SUBSTITUTION_ONE = {"arg1": "arg1"}
+SUBSTITUTION_TWO = {"arg2": "arg2"}
+
+
+@tag("unisender_go")
+@override_settings(ANYMAIL_UNISENDER_GO_API_KEY=None, ANYMAIL_UNISENDER_GO_API_URL="")
+class TestUnisenderGoPayload(SimpleTestCase):
+    def test_unisender_go_payload__full(self):
+        substitutions = {TO_EMAIL: SUBSTITUTION_ONE, OTHER_TO_EMAIL: SUBSTITUTION_TWO}
+        email = AnymailMessage(
+            template_id=TEMPLATE_ID,
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=str(Address(display_name=FROM_NAME, addr_spec=FROM_EMAIL)),
+            to=[
+                str(Address(display_name=TO_NAME, addr_spec=TO_EMAIL)),
+                str(Address(display_name=OTHER_TO_NAME, addr_spec=OTHER_TO_EMAIL)),
+            ],
+            merge_data=substitutions,
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {
+                "to": ", ".join(email.to),
+            },
+            "recipients": [
+                {
+                    "email": TO_EMAIL,
+                    "substitutions": {**SUBSTITUTION_ONE, "to_name": TO_NAME},
+                },
+                {
+                    "email": OTHER_TO_EMAIL,
+                    "substitutions": {**SUBSTITUTION_TWO, "to_name": OTHER_TO_NAME},
+                },
+            ],
+            "subject": SUBJECT,
+            "template_id": TEMPLATE_ID,
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    def test_unisender_go_payload__cc_bcc(self):
+        cc_to_email = "receiver_cc@test.test"
+        bcc_to_email = "receiver_bcc@test.test"
+        email = AnymailMessage(
+            template_id=TEMPLATE_ID,
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=f"{FROM_NAME} <{FROM_EMAIL}>",
+            to=[
+                str(Address(display_name=TO_NAME, addr_spec=TO_EMAIL)),
+                str(Address(display_name=OTHER_TO_NAME, addr_spec=OTHER_TO_EMAIL)),
+            ],
+            cc=[cc_to_email],
+            bcc=[bcc_to_email],
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_headers = {
+            "To": f"{TO_NAME} <{TO_EMAIL}>, {OTHER_TO_NAME} <{OTHER_TO_EMAIL}>",
+            "CC": cc_to_email,
+        }
+        expected_headers = CaseInsensitiveDict(expected_headers)
+        expected_recipients = [
+            {
+                "email": TO_EMAIL,
+                "substitutions": {"to_name": TO_NAME},
+            },
+            {
+                "email": OTHER_TO_EMAIL,
+                "substitutions": {"to_name": OTHER_TO_NAME},
+            },
+            {"email": cc_to_email},
+            {"email": bcc_to_email},
+        ]
+
+        self.assertEqual(payload.data["headers"], expected_headers)
+        self.assertCountEqual(payload.data["recipients"], expected_recipients)
+
+    def test_unisender_go_payload__parse_from__with_name(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=str(Address(display_name=FROM_NAME, addr_spec=FROM_EMAIL)),
+            to=[TO_EMAIL],
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    def test_unisender_go_payload__parse_from__without_name(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=FROM_EMAIL,
+            to=[TO_EMAIL],
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    @override_settings(
+        ANYMAIL={"UNISENDER_GO_SEND_DEFAULTS": {"esp_extra": {"skip_unsubscribe": 1}}},
+    )
+    def test_unisender_go_payload__parse_from__with_unsub__in_settings(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=f"{FROM_NAME} <{FROM_EMAIL}>",
+            to=[TO_EMAIL],
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+            "skip_unsubscribe": 1,
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    @override_settings(
+        ANYMAIL={"UNISENDER_GO_SEND_DEFAULTS": {"esp_extra": {"skip_unsubscribe": 0}}},
+    )
+    def test_unisender_go_payload__parse_from__with_unsub__in_args(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=f"{FROM_NAME} <{FROM_EMAIL}>",
+            to=[TO_EMAIL],
+            esp_extra={"skip_unsubscribe": 1},
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+            "skip_unsubscribe": 1,
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    @override_settings(
+        ANYMAIL={
+            "UNISENDER_GO_SEND_DEFAULTS": {"esp_extra": {"global_language": "en"}}
+        },
+    )
+    def test_unisender_go_payload__parse_from__global_language__in_settings(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=f"{FROM_NAME} <{FROM_EMAIL}>",
+            to=[TO_EMAIL],
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+            "global_language": "en",
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    @override_settings(
+        ANYMAIL={
+            "UNISENDER_GO_SEND_DEFAULTS": {"esp_extra": {"global_language": "fr"}}
+        },
+    )
+    def test_unisender_go_payload__parse_from__global_language__in_args(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=f"{FROM_NAME} <{FROM_EMAIL}>",
+            to=[TO_EMAIL],
+            esp_extra={"global_language": "en"},
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+            "global_language": "en",
+        }
+
+        self.assertEqual(payload.data, expected_payload)
+
+    def test_unisender_go_payload__parse_from__bypass_esp_extra(self):
+        email = AnymailMessage(
+            subject=SUBJECT,
+            merge_global_data=GLOBAL_DATA,
+            from_email=f"{FROM_NAME} <{FROM_EMAIL}>",
+            to=[TO_EMAIL],
+            esp_extra={
+                "bypass_global": 1,
+                "bypass_unavailable": 1,
+                "bypass_unsubscribed": 1,
+                "bypass_complained": 1,
+            },
+        )
+        backend = EmailBackend()
+
+        payload = UnisenderGoPayload(
+            message=email, backend=backend, defaults=backend.send_defaults
+        )
+        expected_payload = {
+            "from_email": FROM_EMAIL,
+            "from_name": FROM_NAME,
+            "global_substitutions": GLOBAL_DATA,
+            "headers": {"to": TO_EMAIL},
+            "recipients": [{"email": TO_EMAIL}],
+            "subject": SUBJECT,
+            "bypass_global": 1,
+            "bypass_unavailable": 1,
+            "bypass_unsubscribed": 1,
+            "bypass_complained": 1,
+        }
+
+        self.assertEqual(payload.data, expected_payload)
--- a/tests/test_unisender_go_webhooks.py
+++ b/tests/test_unisender_go_webhooks.py
@@ -0,0 +1,177 @@
+from __future__ import annotations
+
+import datetime
+import hashlib
+import uuid
+from datetime import timezone
+
+from django.test import RequestFactory, SimpleTestCase, override_settings, tag
+
+from anymail.exceptions import AnymailWebhookValidationFailure
+from anymail.signals import EventType, RejectReason
+from anymail.webhooks.unisender_go import UnisenderGoTrackingWebhookView
+
+EVENT_TYPE = EventType.SENT
+EVENT_TIME = "2015-11-30 15:09:42"
+EVENT_DATETIME = datetime.datetime(2015, 11, 30, 15, 9, 42, tzinfo=timezone.utc)
+JOB_ID = "1a3Q2V-0000OZ-S0"
+DELIVERY_RESPONSE = "550 Spam rejected"
+UNISENDER_TEST_EMAIL = "recipient.email@example.com"
+TEST_API_KEY = "api_key"
+TEST_EMAIL_ID = str(uuid.uuid4())
+UNISENDER_TEST_DEFAULT_EXAMPLE = {
+    "auth": TEST_API_KEY,
+    "events_by_user": [
+        {
+            "user_id": 456,
+            "project_id": "6432890213745872",
+            "project_name": "MyProject",
+            "events": [
+                {
+                    "event_name": "transactional_email_status",
+                    "event_data": {
+                        "job_id": JOB_ID,
+                        "metadata": {"key1": "val1", "anymail_id": TEST_EMAIL_ID},
+                        "email": UNISENDER_TEST_EMAIL,
+                        "status": EVENT_TYPE,
+                        "event_time": EVENT_TIME,
+                        "url": "http://some.url.com",
+                        "delivery_info": {
+                            "delivery_status": "err_delivery_failed",
+                            "destination_response": DELIVERY_RESPONSE,
+                            "user_agent": (
+                                "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 "
+                                "(KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36"
+                            ),
+                            "ip": "111.111.111.111",
+                        },
+                    },
+                },
+                {
+                    "event_name": "transactional_spam_block",
+                    "event_data": {
+                        "block_time": "YYYY-MM-DD HH:MM:SS",
+                        "block_type": "one_smtp",
+                        "domain": "domain_name",
+                        "SMTP_blocks_count": 8,
+                        "domain_status": "blocked",
+                    },
+                },
+            ],
+        }
+    ],
+}
+EXAMPLE_WITHOUT_DELIVERY_INFO = {
+    "auth": "",
+    "events_by_user": [
+        {
+            "events": [
+                {
+                    "event_name": "transactional_email_status",
+                    "event_data": {
+                        "job_id": JOB_ID,
+                        "metadata": {},
+                        "email": UNISENDER_TEST_EMAIL,
+                        "status": EVENT_TYPE,
+                        "event_time": EVENT_TIME,
+                    },
+                }
+            ]
+        }
+    ],
+}
+REQUEST_JSON = '{"auth":"api_key","key":"value"}'
+REQUEST_JSON_MD5 = "8c64386327f53722434f44021a7a0d40"  # md5 hash of REQUEST_JSON
+REQUEST_DATA_AUTH = {"auth": REQUEST_JSON_MD5, "key": "value"}
+
+
+def _request_json_to_dict_with_hashed_key(request_json: bytes) -> dict[str, str]:
+    new_auth = hashlib.md5(request_json).hexdigest()
+    return {"auth": new_auth, "key": "value"}
+
+
+@tag("unisender_go")
+class TestUnisenderGoWebhooks(SimpleTestCase):
+    def test_sent_event(self):
+        request = RequestFactory().post(
+            path="/",
+            data=UNISENDER_TEST_DEFAULT_EXAMPLE,
+            content_type="application/json",
+        )
+        view = UnisenderGoTrackingWebhookView()
+
+        events = view.parse_events(request)
+        event = events[0]
+
+        self.assertEqual(len(events), 1)
+        self.assertEqual(event.event_type, EVENT_TYPE)
+        self.assertEqual(event.timestamp, EVENT_DATETIME)
+        self.assertIsNone(event.event_id)
+        self.assertEqual(event.recipient, UNISENDER_TEST_EMAIL)
+        self.assertEqual(event.reject_reason, RejectReason.OTHER)
+        self.assertEqual(event.mta_response, DELIVERY_RESPONSE)
+        self.assertDictEqual(event.metadata, {"key1": "val1"})
+
+    def test_without_delivery_info(self):
+        request = RequestFactory().post(
+            path="/",
+            data=EXAMPLE_WITHOUT_DELIVERY_INFO,
+            content_type="application/json",
+        )
+        view = UnisenderGoTrackingWebhookView()
+
+        events = view.parse_events(request)
+
+        self.assertEqual(len(events), 1)
+        # Without metadata["anymail_id"], message_id uses the job_id.
+        # (This covers messages sent with "UNISENDER_GO_GENERATE_MESSAGE_ID": False.)
+        self.assertEqual(events[0].message_id, JOB_ID)
+
+    @override_settings(ANYMAIL_UNISENDER_GO_API_KEY=TEST_API_KEY)
+    def test_check_authorization(self):
+        """Asserts that nothing is failing"""
+        request_data = _request_json_to_dict_with_hashed_key(
+            b'{"auth":"api_key","key":"value"}',
+        )
+        request = RequestFactory().post(
+            path="/", data=request_data, content_type="application/json"
+        )
+        view = UnisenderGoTrackingWebhookView()
+
+        view.validate_request(request)
+
+    @override_settings(ANYMAIL_UNISENDER_GO_API_KEY=TEST_API_KEY)
+    def test_check_authorization__fail__ordinar_quoters(self):
+        request_json = b"{'auth':'api_key','key':'value'}"
+        request_data = _request_json_to_dict_with_hashed_key(request_json)
+        request = RequestFactory().post(
+            path="/", data=request_data, content_type="application/json"
+        )
+        view = UnisenderGoTrackingWebhookView()
+
+        with self.assertRaises(AnymailWebhookValidationFailure):
+            view.validate_request(request)
+
+    @override_settings(ANYMAIL_UNISENDER_GO_API_KEY=TEST_API_KEY)
+    def test_check_authorization__fail__spaces_after_semicolon(self):
+        request_json = b'{"auth": "api_key","key": "value"}'
+        request_data = _request_json_to_dict_with_hashed_key(request_json)
+        request = RequestFactory().post(
+            path="/", data=request_data, content_type="application/json"
+        )
+        view = UnisenderGoTrackingWebhookView()
+
+        with self.assertRaises(AnymailWebhookValidationFailure):
+            view.validate_request(request)
+
+    @override_settings(ANYMAIL_UNISENDER_GO_API_KEY=TEST_API_KEY)
+    def test_check_authorization__fail__spaces_after_comma(self):
+        request_json = b'{"auth":"api_key", "key":"value"}'
+        request_data = _request_json_to_dict_with_hashed_key(request_json)
+        request = RequestFactory().post(
+            path="/", data=request_data, content_type="application/json"
+        )
+        view = UnisenderGoTrackingWebhookView()
+
+        with self.assertRaises(AnymailWebhookValidationFailure):
+            view.validate_request(request)
--- a/tox.ini
+++ b/tox.ini
@@ -67,6 +67,7 @@ setenv =
    postmark: ANYMAIL_ONLY_TEST=postmark
    resend: ANYMAIL_ONLY_TEST=resend
    sendgrid: ANYMAIL_ONLY_TEST=sendgrid
+    unisender_go: ANYMAIL_ONLY_TEST=unisender_go
    sendinblue: ANYMAIL_ONLY_TEST=sendinblue
    sparkpost: ANYMAIL_ONLY_TEST=sparkpost
 ignore_outcome =