Add Mailgun backend

2025-12-20 11:51:05 -05:00 · 2016-03-07 18:07:48 -08:00
parent 4ad2af2469
commit d1d41badc8
13 changed files with 1103 additions and 64 deletions
--- a/anymail/backends/base.py
+++ b/anymail/backends/base.py
@@ -5,45 +5,10 @@ from django.core.mail.backends.base import BaseEmailBackend
 from django.utils.timezone import is_naive, get_current_timezone, make_aware, utc

 from ..exceptions import AnymailError, AnymailUnsupportedFeature, AnymailRecipientsRefused
+from ..message import AnymailStatus
 from ..utils import Attachment, ParsedEmail, UNSET, combine, last, get_anymail_setting


-# The AnymailStatus* stuff should get moved to an anymail.message module
-ANYMAIL_STATUSES = [
-    'sent',  # the ESP has sent the message (though it may or may not get delivered)
-    'queued',  # the ESP will try to send the message later
-    'invalid',  # the recipient email was not valid
-    'rejected',  # the recipient is blacklisted
-    'unknown',  # anything else
-]
-
-
-class AnymailRecipientStatus(object):
-    """Information about an EmailMessage's send status for a single recipient"""
-
-    def __init__(self, message_id, status):
-        self.message_id = message_id  # ESP message id
-        self.status = status  # one of ANYMAIL_STATUSES, or None for not yet sent to ESP
-
-
-class AnymailStatus(object):
-    """Information about an EmailMessage's send status for all recipients"""
-
-    def __init__(self):
-        self.message_id = None  # set of ESP message ids across all recipients, or bare id if only one, or None
-        self.status = None  # set of ANYMAIL_STATUSES across all recipients, or None for not yet sent to ESP
-        self.recipients = {}  # per-recipient: { email: AnymailRecipientStatus, ... }
-        self.esp_response = None
-
-    def set_recipient_status(self, recipients):
-        self.recipients.update(recipients)
-        recipient_statuses = self.recipients.values()
-        self.message_id = set([recipient.message_id for recipient in recipient_statuses])
-        if len(self.message_id) == 1:
-            self.message_id = self.message_id.pop()  # de-set-ify if single message_id
-        self.status = set([recipient.status for recipient in recipient_statuses])
-
-
 class AnymailBaseBackend(BaseEmailBackend):
    """
    Base Anymail email backend
--- a/anymail/backends/mailgun.py
+++ b/anymail/backends/mailgun.py
@@ -0,0 +1,155 @@
+from datetime import datetime
+
+from ..exceptions import AnymailRequestsAPIError, AnymailError
+from ..message import AnymailRecipientStatus
+from ..utils import get_anymail_setting, rfc2822date
+
+from .base_requests import AnymailRequestsBackend, RequestsPayload
+
+
+class MailgunBackend(AnymailRequestsBackend):
+    """
+    Mailgun API Email Backend
+    """
+
+    def __init__(self, **kwargs):
+        """Init options from Django settings"""
+        self.api_key = get_anymail_setting('MAILGUN_API_KEY', allow_bare=True)
+        api_url = get_anymail_setting("MAILGUN_API_URL", "https://api.mailgun.net/v3")
+        if not api_url.endswith("/"):
+            api_url += "/"
+        super(MailgunBackend, self).__init__(api_url, **kwargs)
+
+    def build_message_payload(self, message, defaults):
+        return MailgunPayload(message, defaults, self)
+
+    def parse_recipient_status(self, response, payload, message):
+        # The *only* 200 response from Mailgun seems to be:
+        #     {
+        #       "id": "<20160306015544.116301.25145@example.org>",
+        #       "message": "Queued. Thank you."
+        #     }
+        #
+        # That single message id applies to all recipients.
+        # The only way to detect rejected, etc. is via webhooks.
+        # (*Any* invalid recipient addresses will generate a 400 API error)
+        parsed_response = self.deserialize_json_response(response, payload, message)
+        try:
+            message_id = parsed_response["id"]
+            mailgun_message = parsed_response["message"]
+        except (KeyError, TypeError):
+            raise AnymailRequestsAPIError("Invalid Mailgun API response format",
+                                          email_message=message, payload=payload, response=response)
+        if not mailgun_message.startswith("Queued"):
+            raise AnymailRequestsAPIError("Unrecognized Mailgun API message '%s'" % mailgun_message,
+                                          email_message=message, payload=payload, response=response)
+        # Simulate a per-recipient status of "queued":
+        status = AnymailRecipientStatus(message_id=message_id, status="queued")
+        return {recipient.email: status for recipient in payload.all_recipients}
+
+
+class MailgunPayload(RequestsPayload):
+
+    def __init__(self, message, defaults, backend, *args, **kwargs):
+        auth = ("api", backend.api_key)
+        self.sender_domain = None
+        self.all_recipients = []  # used for backend.parse_recipient_status
+        super(MailgunPayload, self).__init__(message, defaults, backend, auth=auth, *args, **kwargs)
+
+    def get_api_endpoint(self):
+        if self.sender_domain is None:
+            raise AnymailError("Cannot call Mailgun unknown sender domain. "
+                               "Either provide valid `from_email`, "
+                               "or set `message.esp_extra={'sender_domain': 'example.com'}`",
+                               backend=self.backend, email_message=self.message, payload=self)
+        return "%s/messages" % self.sender_domain
+
+    #
+    # Payload construction
+    #
+
+    def init_payload(self):
+        self.data = {}   # {field: [multiple, values]}
+        self.files = []  # [(field, multiple), (field, values)]
+
+    def set_from_email(self, email):
+        self.data["from"] = str(email)
+        if self.sender_domain is None:
+            # try to intuit sender_domain from from_email
+            try:
+                _, domain = email.email.split('@')
+                self.sender_domain = domain
+            except ValueError:
+                pass
+
+    def set_recipients(self, recipient_type, emails):
+        assert recipient_type in ["to", "cc", "bcc"]
+        if emails:
+            self.data[recipient_type] = [str(email) for email in emails]
+            self.all_recipients += emails  # used for backend.parse_recipient_status
+
+    def set_subject(self, subject):
+        self.data["subject"] = subject
+
+    def set_reply_to(self, emails):
+        if emails:
+            reply_to = ", ".join([str(email) for email in emails])
+            self.data["h:Reply-To"] = reply_to
+
+    def set_extra_headers(self, headers):
+        for key, value in headers.items():
+            self.data["h:%s" % key] = value
+
+    def set_text_body(self, body):
+        self.data["text"] = body
+
+    def set_html_body(self, body):
+        if "html" in self.data:
+            # second html body could show up through multiple alternatives, or html body + alternative
+            self.unsupported_feature("multiple html parts")
+        self.data["html"] = body
+
+    def add_attachment(self, attachment):
+        # http://docs.python-requests.org/en/v2.4.3/user/advanced/#post-multiple-multipart-encoded-files
+        field = "inline" if attachment.inline else "attachment"
+        self.files.append(
+            (field, (attachment.name, attachment.content, attachment.mimetype))
+        )
+
+    def set_metadata(self, metadata):
+        # The Mailgun docs are a little unclear on whether to send each var as a separate v: field,
+        # or to send a single 'v:my-custom-data' field with a json blob of all vars.
+        # (https://documentation.mailgun.com/user_manual.html#attaching-data-to-messages)
+        # From experimentation, it seems like the first option works:
+        for key, value in metadata.items():
+            # Ensure the value is json-serializable (for Mailgun storage)
+            json = self.serialize_json(value)  # will raise AnymailSerializationError
+            # Special case: a single string value should be sent bare (without quotes),
+            # because Mailgun will add quotes when querying the value as json.
+            if json.startswith('"'):  # only a single string could be serialized as "...
+                json = value
+            self.data["v:%s" % key] = json
+
+    def set_send_at(self, send_at):
+        # Mailgun expects RFC-2822 format dates
+        # (BasePayload has converted most date-like values to datetime by now;
+        # if the caller passes a string, they'll need to format it themselves.)
+        if isinstance(send_at, datetime):
+            send_at = rfc2822date(send_at)
+        self.data["o:deliverytime"] = send_at
+
+    def set_tags(self, tags):
+        self.data["o:tag"] = tags
+
+    def set_track_clicks(self, track_clicks):
+        # Mailgun also supports an "htmlonly" option, which Anymail doesn't offer
+        self.data["o:tracking-clicks"] = "yes" if track_clicks else "no"
+
+    def set_track_opens(self, track_opens):
+        self.data["o:tracking-opens"] = "yes" if track_opens else "no"
+
+    def set_esp_extra(self, extra):
+        self.data.update(extra)
+        # Allow override of sender_domain via esp_extra
+        # (but pop it out of params to send to Mailgun)
+        self.sender_domain = self.data.pop("sender_domain", self.sender_domain)
--- a/anymail/backends/mandrill.py
+++ b/anymail/backends/mandrill.py
@@ -1,7 +1,7 @@
 from datetime import datetime

-from anymail.backends.base import AnymailRecipientStatus, ANYMAIL_STATUSES
 from ..exceptions import AnymailRequestsAPIError
+from ..message import AnymailRecipientStatus, ANYMAIL_STATUSES
 from ..utils import last, combine, get_anymail_setting

 from .base_requests import AnymailRequestsBackend, RequestsPayload
--- a/anymail/message.py
+++ b/anymail/message.py
@@ -0,0 +1,83 @@
+from email.mime.image import MIMEImage
+
+from django.core.mail import EmailMessage, EmailMultiAlternatives, make_msgid
+
+from .utils import UNSET
+
+
+class AnymailMessageMixin(object):
+    """Mixin for EmailMessage that exposes Anymail features.
+
+    Use of this mixin is optional. You can always just set Anymail
+    attributes on any EmailMessage.
+
+    (The mixin can be helpful with type checkers and other development
+    tools that complain about accessing Anymail's added attributes
+    on a regular EmailMessage.)
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.esp_extra = kwargs.pop('esp_extra', UNSET)
+        self.metadata = kwargs.pop('metadata', UNSET)
+        self.send_at = kwargs.pop('send_at', UNSET)
+        self.tags = kwargs.pop('tags', UNSET)
+        self.track_clicks = kwargs.pop('track_clicks', UNSET)
+        self.track_opens = kwargs.pop('track_opens', UNSET)
+        self.anymail_status = None
+
+        # noinspection PyArgumentList
+        super(AnymailMessageMixin, self).__init__(*args, **kwargs)
+
+    def attach_inline_image(self, content, subtype=None, idstring="img", domain=None):
+        """Add inline image and return its content id"""
+        assert isinstance(self, EmailMessage)
+        return attach_inline_image(self, content, subtype, idstring, domain)
+
+
+class AnymailMessage(AnymailMessageMixin, EmailMultiAlternatives):
+    pass
+
+
+def attach_inline_image(message, content, subtype=None, idstring="img", domain=None):
+    """Add inline image to an EmailMessage, and return its content id"""
+    cid = make_msgid(idstring, domain)  # Content ID per RFC 2045 section 7 (with <...>)
+    image = MIMEImage(content, subtype)
+    image.add_header('Content-ID', cid)
+    message.attach(image)
+    return cid[1:-1]  # Without <...>, for use as the <img> tag src
+
+
+ANYMAIL_STATUSES = [
+    'sent',  # the ESP has sent the message (though it may or may not get delivered)
+    'queued',  # the ESP will try to send the message later
+    'invalid',  # the recipient email was not valid
+    'rejected',  # the recipient is blacklisted
+    'failed',  # the attempt to send failed for some other reason
+    'unknown',  # anything else
+]
+
+
+class AnymailRecipientStatus(object):
+    """Information about an EmailMessage's send status for a single recipient"""
+
+    def __init__(self, message_id, status):
+        self.message_id = message_id  # ESP message id
+        self.status = status  # one of ANYMAIL_STATUSES, or None for not yet sent to ESP
+
+
+class AnymailStatus(object):
+    """Information about an EmailMessage's send status for all recipients"""
+
+    def __init__(self):
+        self.message_id = None  # set of ESP message ids across all recipients, or bare id if only one, or None
+        self.status = None  # set of ANYMAIL_STATUSES across all recipients, or None for not yet sent to ESP
+        self.recipients = {}  # per-recipient: { email: AnymailRecipientStatus, ... }
+        self.esp_response = None
+
+    def set_recipient_status(self, recipients):
+        self.recipients.update(recipients)
+        recipient_statuses = self.recipients.values()
+        self.message_id = set([recipient.message_id for recipient in recipient_statuses])
+        if len(self.message_id) == 1:
+            self.message_id = self.message_id.pop()  # de-set-ify if single message_id
+        self.status = set([recipient.status for recipient in recipient_statuses])
--- a/anymail/tests/init.py
+++ b/anymail/tests/init.py
@@ -1,3 +1,8 @@
+# Exposing all TestCases at the 'tests' module level
+# is required by the old (<=1.5) DjangoTestSuiteRunner.
+
+from .test_mailgun_backend import *
+
 from .test_mandrill_integration import *
 from .test_mandrill_send import *
 from .test_mandrill_send_template import *
--- a/anymail/tests/mock_backend.py
+++ b/anymail/tests/mock_backend.py
@@ -47,9 +47,9 @@ class DjrillBackendMockAPITestCase(TestCase):
            raise AssertionError("Mandrill API was not called")
        (args, kwargs) = self.mock_post.call_args
        try:
-            post_url = kwargs.get('url', None) or args[1]
+            post_url = kwargs.get('url', None) or args[2]
        except IndexError:
-            raise AssertionError("requests.post was called without an url (?!)")
+            raise AssertionError("requests.Session.request was called without an url (?!)")
        if not post_url.endswith(endpoint):
            raise AssertionError(
                "requests.post was not called on %s\n(It was called on %s)"
@@ -64,9 +64,9 @@ class DjrillBackendMockAPITestCase(TestCase):
            raise AssertionError("Mandrill API was not called")
        (args, kwargs) = self.mock_post.call_args
        try:
-            post_data = kwargs.get('data', None) or args[2]
+            post_data = kwargs.get('data', None) or args[4]
        except IndexError:
-            raise AssertionError("requests.post was called without data")
+            raise AssertionError("requests.Session.request was called without data")
        return json.loads(post_data)


--- a/anymail/tests/mock_requests_backend.py
+++ b/anymail/tests/mock_requests_backend.py
@@ -0,0 +1,103 @@
+import json
+
+from django.test import SimpleTestCase
+import requests
+import six
+from mock import patch
+
+from .utils import AnymailTestMixin
+
+UNSET = object()
+
+
+class RequestsBackendMockAPITestCase(SimpleTestCase, AnymailTestMixin):
+    """TestCase that uses Djrill EmailBackend with a mocked Mandrill API"""
+
+    DEFAULT_RAW_RESPONSE = b"""{"subclass": "should override"}"""
+
+    class MockResponse(requests.Response):
+        """requests.request return value mock sufficient for testing"""
+        def __init__(self, status_code=200, raw=b"RESPONSE", encoding='utf-8'):
+            super(RequestsBackendMockAPITestCase.MockResponse, self).__init__()
+            self.status_code = status_code
+            self.encoding = encoding
+            self.raw = six.BytesIO(raw)
+
+    def setUp(self):
+        super(RequestsBackendMockAPITestCase, self).setUp()
+        self.patch = patch('requests.Session.request', autospec=True)
+        self.mock_request = self.patch.start()
+        self.addCleanup(self.patch.stop)
+        self.set_mock_response()
+
+    def set_mock_response(self, status_code=200, raw=UNSET, encoding='utf-8'):
+        if raw is UNSET:
+            raw = self.DEFAULT_RAW_RESPONSE
+        mock_response = self.MockResponse(status_code, raw, encoding)
+        self.mock_request.return_value = mock_response
+        return mock_response
+
+    def assert_esp_called(self, url, method="POST"):
+        """Verifies the (mock) ESP API was called on endpoint.
+
+        url can be partial, and is just checked against the end of the url requested"
+        """
+        # This assumes the last (or only) call to requests.Session.request is the API call of interest.
+        if self.mock_request.call_args is None:
+            raise AssertionError("No ESP API was called")
+        (args, kwargs) = self.mock_request.call_args
+        try:
+            actual_method = kwargs.get('method', None) or args[1]
+            actual_url = kwargs.get('url', None) or args[2]
+        except IndexError:
+            raise AssertionError("API was called without a method or url (?!)")
+        if actual_method != method:
+            raise AssertionError("API was not called using %s. (%s was used instead.)"
+                                 % (method, actual_method))
+        if not actual_url.endswith(url):
+            raise AssertionError("API was not called at %s\n(It was called at %s)"
+                                 % (url, actual_url))
+
+    def get_api_call_arg(self, kwarg, pos, required=True):
+        """Returns an argument passed to the mock ESP API.
+
+        Fails test if API wasn't called.
+        """
+        if self.mock_request.call_args is None:
+            raise AssertionError("API was not called")
+        (args, kwargs) = self.mock_request.call_args
+        try:
+            return kwargs.get(kwarg, None) or args[pos]
+        except IndexError:
+            if required:
+                raise AssertionError("API was called without required %s" % kwarg)
+            else:
+                return None
+
+    def get_api_call_params(self, required=True):
+        """Returns the query params sent to the mock ESP API."""
+        return self.get_api_call_arg('params', 3, required)
+
+    def get_api_call_data(self, required=True):
+        """Returns the raw data sent to the mock ESP API."""
+        return self.get_api_call_arg('data', 4, required)
+
+    def get_api_call_json(self, required=True):
+        """Returns the data sent to the mock ESP API, json-parsed"""
+        return json.loads(self.get_api_call_data(required))
+
+    def get_api_call_headers(self, required=True):
+        """Returns the headers sent to the mock ESP API"""
+        return self.get_api_call_arg('headers', 5, required)
+
+    def get_api_call_files(self, required=True):
+        """Returns the files sent to the mock ESP API"""
+        return self.get_api_call_arg('files', 7, required)
+
+    def get_api_call_auth(self, required=True):
+        """Returns the auth sent to the mock ESP API"""
+        return self.get_api_call_arg('auth', 8, required)
+
+    def assert_esp_not_called(self, msg=None):
+        if self.mock_request.called:
+            raise AssertionError(msg or "ESP API was called and shouldn't have been")
--- a/anymail/tests/test_mailgun_backend.py
+++ b/anymail/tests/test_mailgun_backend.py
@@ -0,0 +1,508 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import unicode_literals
+
+from datetime import date, datetime
+from decimal import Decimal
+from email.mime.base import MIMEBase
+from email.mime.image import MIMEImage
+
+from django.core import mail
+from django.core.exceptions import ImproperlyConfigured
+from django.test import SimpleTestCase
+from django.test.utils import override_settings
+from django.utils.timezone import get_fixed_timezone, override as override_current_timezone
+
+from anymail.exceptions import AnymailAPIError, AnymailSerializationError, AnymailUnsupportedFeature
+from anymail.message import attach_inline_image
+
+from .mock_requests_backend import RequestsBackendMockAPITestCase
+from .utils import sample_image_content, sample_image_path, SAMPLE_IMAGE_FILENAME, AnymailTestMixin
+
+
+@override_settings(EMAIL_BACKEND='anymail.backends.mailgun.MailgunBackend',
+                   ANYMAIL={'MAILGUN_API_KEY': 'test_api_key'})
+class MailgunBackendMockAPITestCase(RequestsBackendMockAPITestCase):
+    DEFAULT_RAW_RESPONSE = b"""{
+        "id": "<20160306015544.116301.25145@example.com>",
+        "message": "Queued. Thank you."
+    }"""
+
+    def setUp(self):
+        super(MailgunBackendMockAPITestCase, self).setUp()
+        # Simple message useful for many tests
+        self.message = mail.EmailMultiAlternatives('Subject', 'Text Body', 'from@example.com', ['to@example.com'])
+
+
+class MailgunBackendStandardEmailTests(MailgunBackendMockAPITestCase):
+    """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@example.com', ['to@example.com'], fail_silently=False)
+        self.assert_esp_called('/example.com/messages')
+        auth = self.get_api_call_auth()
+        self.assertEqual(auth, ('api', 'test_api_key'))
+        data = self.get_api_call_data()
+        self.assertEqual(data['subject'], "Subject here")
+        self.assertEqual(data['text'], "Here is the message.")
+        self.assertEqual(data['from'], "from@example.com")
+        self.assertEqual(data['to'], ["to@example.com"])
+
+    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_data()
+        self.assertEqual(data['from'], "From Name <from@example.com>")
+        self.assertEqual(data['to'], ['Recipient #1 <to1@example.com>', 'to2@example.com'])
+        self.assertEqual(data['cc'], ['Carbon Copy <cc1@example.com>', 'cc2@example.com'])
+        self.assertEqual(data['bcc'], ['Blind Copy <bcc1@example.com>', 'bcc2@example.com'])
+
+    def test_email_message(self):
+        email = mail.EmailMessage(
+            'Subject', 'Body goes here', 'from@example.com',
+            ['to1@example.com', 'Also To <to2@example.com>'],
+            bcc=['bcc1@example.com', 'Also BCC <bcc2@example.com>'],
+            cc=['cc1@example.com', 'Also CC <cc2@example.com>'],
+            headers={'Reply-To': 'another@example.com',
+                     'X-MyHeader': 'my value',
+                     'Message-ID': 'mycustommsgid@example.com'})
+        email.send()
+        data = self.get_api_call_data()
+        self.assertEqual(data['subject'], "Subject")
+        self.assertEqual(data['text'], "Body goes here")
+        self.assertEqual(data['from'], "from@example.com")
+        self.assertEqual(data['to'], ['to1@example.com', 'Also To <to2@example.com>'])
+        self.assertEqual(data['bcc'], ['bcc1@example.com', 'Also BCC <bcc2@example.com>'])
+        self.assertEqual(data['cc'], ['cc1@example.com', 'Also CC <cc2@example.com>'])
+        self.assertEqual(data['h:Reply-To'], "another@example.com")
+        self.assertEqual(data['h:X-MyHeader'], 'my value')
+        self.assertEqual(data['h:Message-ID'], 'mycustommsgid@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_data()
+        self.assertEqual(data['text'], text_content)
+        self.assertEqual(data['html'], html_content)
+        # Don't accidentally send the html part as an attachment:
+        files = self.get_api_call_files(required=False)
+        self.assertIsNone(files)
+
+    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_data()
+        self.assertNotIn('text', data)
+        self.assertEqual(data['html'], html_content)
+
+    def test_reply_to(self):
+        # reply_to is new in Django 1.8 -- before that, you can simply include it in headers
+        try:
+            # noinspection PyArgumentList
+            email = mail.EmailMessage('Subject', 'Body goes here', 'from@example.com', ['to1@example.com'],
+                                      reply_to=['reply@example.com', 'Other <reply2@example.com>'],
+                                      headers={'X-Other': 'Keep'})
+        except TypeError:
+            # Pre-Django 1.8
+            return self.skipTest("Django version doesn't support EmailMessage(reply_to)")
+        email.send()
+        data = self.get_api_call_data()
+        self.assertEqual(data['h:Reply-To'], 'reply@example.com, Other <reply2@example.com>')
+        self.assertEqual(data['h:X-Other'], 'Keep')  # don't lose other headers
+
+    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()
+        files = self.get_api_call_files()
+        attachments = [value for (field, value) in files if field == 'attachment']
+        self.assertEqual(len(attachments), 3)
+        self.assertEqual(attachments[0], ('test.txt', text_content, 'text/plain'))
+        self.assertEqual(attachments[1], ('test.png', png_content, 'image/png'))  # type inferred from filename
+        self.assertEqual(attachments[2], (None, pdf_content, 'application/pdf'))  # no filename
+        # Make sure the image attachment is not treated as embedded:
+        inlines = [value for (field, value) in files if field == 'inline']
+        self.assertEqual(len(inlines), 0)
+
+    def test_unicode_attachment_correctly_decoded(self):
+        # Slight modification from the Django unicode docs:
+        # http://django.readthedocs.org/en/latest/ref/unicode.html#email
+        self.message.attach("Une pièce jointe.html", '<p>\u2019</p>', mimetype='text/html')
+        self.message.send()
+        files = self.get_api_call_files()
+        attachments = [value for (field, value) in files if field == 'attachment']
+        self.assertEqual(len(attachments), 1)
+
+    def test_embedded_images(self):
+        image_data = sample_image_content()  # Read from a png file
+        cid = attach_inline_image(self.message, image_data)
+        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_data()
+        self.assertEqual(data['html'], html_content)
+
+        files = self.get_api_call_files()
+        inlines = [value for (field, value) in files if field == 'inline']
+        self.assertEqual(len(inlines), 1)
+        self.assertEqual(inlines[0], (cid, image_data, "image/png"))  # filename is cid; type is guessed
+        # Make sure neither the html nor the inline image is treated as an attachment:
+        attachments = [value for (field, value) in files if field == 'attachment']
+        self.assertEqual(len(attachments), 0)
+
+    def test_attached_images(self):
+        image_filename = SAMPLE_IMAGE_FILENAME
+        image_path = sample_image_path(image_filename)
+        image_data = sample_image_content(image_filename)
+
+        self.message.attach_file(image_path)  # option 1: attach as a file
+
+        image = MIMEImage(image_data)  # option 2: construct the MIMEImage and attach it directly
+        self.message.attach(image)
+
+        self.message.send()
+        files = self.get_api_call_files()
+        attachments = [value for (field, value) in files if field == 'attachment']
+        self.assertEqual(len(attachments), 2)
+        self.assertEqual(attachments[0], (image_filename, image_data, 'image/png'))
+        self.assertEqual(attachments[1], (None, image_data, 'image/png'))  # name unknown -- not attached as file
+        # Make sure the image attachments are not treated as inline:
+        inlines = [value for (field, value) in files if field == 'inline']
+        self.assertEqual(len(inlines), 0)
+
+    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_html_alternative(self):
+        # Only html alternatives allowed
+        self.message.attach_alternative("{'not': 'allowed'}", "application/json")
+        with self.assertRaises(AnymailUnsupportedFeature):
+            self.message.send()
+
+    def test_alternatives_fail_silently(self):
+        # Make sure fail_silently is respected
+        self.message.attach_alternative("{'not': 'allowed'}", "application/json")
+        sent = self.message.send(fail_silently=True)
+        self.assert_esp_not_called("API should not be called when send fails silently")
+        self.assertEqual(sent, 0)
+
+    def test_suppress_empty_address_lists(self):
+        """Empty to, cc, bcc, and reply_to shouldn't generate empty headers"""
+        self.message.send()
+        data = self.get_api_call_data()
+        self.assertNotIn('cc', data)
+        self.assertNotIn('bcc', data)
+        self.assertNotIn('h:Reply-To', data)
+
+        # Test empty `to` -- but send requires at least one recipient somewhere (like cc)
+        self.message.to = []
+        self.message.cc = ['cc@example.com']
+        self.message.send()
+        data = self.get_api_call_data()
+        self.assertNotIn('to', data)
+
+    def test_api_failure(self):
+        self.set_mock_response(status_code=400)
+        with self.assertRaises(AnymailAPIError):
+            sent = mail.send_mail('Subject', 'Body', 'from@example.com', ['to@example.com'])
+            self.assertEqual(sent, 0)
+
+        # 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"""
+        # JSON error response:
+        error_response = b"""{"message": "Helpful explanation from your ESP"}"""
+        self.set_mock_response(status_code=400, raw=error_response)
+        with self.assertRaisesMessage(AnymailAPIError, "Helpful explanation from your ESP"):
+            self.message.send()
+
+        # Non-JSON error response:
+        self.set_mock_response(status_code=500, raw=b"Invalid API key")
+        with self.assertRaisesMessage(AnymailAPIError, "Invalid API key"):
+            self.message.send()
+
+        # No content in the error response:
+        self.set_mock_response(status_code=502, raw=None)
+        with self.assertRaises(AnymailAPIError):
+            self.message.send()
+
+
+class MailgunBackendAnymailFeatureTests(MailgunBackendMockAPITestCase):
+    """Test backend support for Anymail added features"""
+
+    def test_metadata(self):
+        self.message.metadata = {'user_id': "12345", 'items': ['mail', 'gun']}
+        self.message.send()
+        data = self.get_api_call_data()
+        # note values get serialized to json:
+        self.assertEqual(data['v:user_id'], '12345')  # simple values are transmitted as-is
+        self.assertEqual(data['v:items'], '["mail", "gun"]')  # complex values get json-serialized
+
+    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-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_data()
+            self.assertEqual(data['o:deliverytime'], "Fri, 04 Mar 2016 13:06:07 GMT")  # 05:06 UTC-8 == 13:06 UTC
+
+            # 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_data()
+            self.assertEqual(data['o:deliverytime'], "Tue, 11 Oct 2022 06:13:14 GMT")  # 12:13 UTC+6 == 06:13 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_data()
+            self.assertEqual(data['o:deliverytime'], "Fri, 21 Oct 2022 18:00:00 GMT")  # 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_data()
+            self.assertEqual(data['o:deliverytime'], "Fri, 06 May 2022 07:08:09 GMT")
+
+            # String passed unchanged (this is *not* portable between ESPs)
+            self.message.send_at = "Thu, 13 Oct 2022 18:02:00 GMT"
+            self.message.send()
+            data = self.get_api_call_data()
+            self.assertEqual(data['o:deliverytime'], "Thu, 13 Oct 2022 18:02:00 GMT")
+
+    def test_tags(self):
+        self.message.tags = ["receipt", "repeat-user"]
+        self.message.send()
+        data = self.get_api_call_data()
+        self.assertEqual(data['o:tag'], ["receipt", "repeat-user"])
+
+    def test_tracking(self):
+        # Test one way...
+        self.message.track_opens = True
+        self.message.track_clicks = False
+        self.message.send()
+        data = self.get_api_call_data()
+        self.assertEqual(data['o:tracking-opens'], 'yes')
+        self.assertEqual(data['o:tracking-clicks'], 'no')
+
+        # ...and the opposite way
+        self.message.track_opens = False
+        self.message.track_clicks = True
+        self.message.send()
+        data = self.get_api_call_data()
+        self.assertEqual(data['o:tracking-opens'], 'no')
+        self.assertEqual(data['o:tracking-clicks'], 'yes')
+
+    def test_sender_domain(self):
+        """Mailgun send domain can come from from_email or esp_extra"""
+        # You could also use ANYMAIL_SEND_DEFAULTS={'esp_extra': {'sender_domain': 'your-domain.com'}}
+        # (The mailgun_integration_tests do that.)
+        self.message.from_email = "Test From <from@from-email.example.com>"
+        self.message.send()
+        self.assert_esp_called('/from-email.example.com/messages')  # API url includes the sender-domain
+
+        self.message.esp_extra = {'sender_domain': 'esp-extra.example.com'}
+        self.message.send()
+        self.assert_esp_called('/esp-extra.example.com/messages')  # overrides from_email
+
+    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()
+        self.assert_esp_called('/example.com/messages')
+        data = self.get_api_call_data()
+        mailgun_fields = {key: value for key, value in data.items()
+                          if key.startswith('o:') or key.startswith('v:')}
+        self.assertEqual(mailgun_fields, {})
+
+    # noinspection PyUnresolvedReferences
+    def test_send_attaches_anymail_status(self):
+        """ The anymail_status should be attached to the message when it is sent """
+        response_content = b"""{
+            "id": "<12345.67890@example.com>",
+            "message": "Queued. Thank you."
+        }"""
+        self.set_mock_response(raw=response_content)
+        msg = mail.EmailMessage('Subject', 'Message', 'from@example.com', ['to1@example.com'],)
+        sent = msg.send()
+        self.assertEqual(sent, 1)
+        self.assertEqual(msg.anymail_status.status, {'queued'})
+        self.assertEqual(msg.anymail_status.message_id, '<12345.67890@example.com>')
+        self.assertEqual(msg.anymail_status.recipients['to1@example.com'].status, 'queued')
+        self.assertEqual(msg.anymail_status.recipients['to1@example.com'].message_id, '<12345.67890@example.com>')
+        self.assertEqual(msg.anymail_status.esp_response.content, response_content)
+
+    # 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)
+
+    # noinspection PyUnresolvedReferences
+    def test_send_unparsable_response(self):
+        """If the send succeeds, but a non-JSON API response, should raise an API exception"""
+        mock_response = self.set_mock_response(status_code=200,
+                                               raw=b"yikes, this isn't a real response")
+        with self.assertRaises(AnymailAPIError):
+            self.message.send()
+        self.assertIsNone(self.message.anymail_status.status)
+        self.assertIsNone(self.message.anymail_status.message_id)
+        self.assertEqual(self.message.anymail_status.recipients, {})
+        self.assertEqual(self.message.anymail_status.esp_response, mock_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()
+            print(self.get_api_call_data())
+        err = cm.exception
+        self.assertIsInstance(err, TypeError)  # compatibility with json.dumps
+        self.assertIn("Don't know how to send this data to Mailgun", str(err))  # our added context
+        self.assertIn("Decimal('19.99') is not JSON serializable", str(err))  # original message
+
+
+class MailgunBackendRecipientsRefusedTests(MailgunBackendMockAPITestCase):
+    """Should raise AnymailRecipientsRefused when *all* recipients are rejected or invalid"""
+
+    # Mailgun doesn't check email bounce or complaint lists at time of send --
+    # it always just queues the message. You'll need to listen for the "rejected"
+    # and "failed" events to detect refused recipients.
+
+    # The one exception is a completely invalid email, which will return a 400 response
+    # and show up as an AnymailAPIError at send time.
+    INVALID_TO_RESPONSE = b"""{
+        "message": "'to' parameter is not a valid address. please check documentation"
+    }"""
+
+    def test_invalid_email(self):
+        self.set_mock_response(status_code=400, raw=self.INVALID_TO_RESPONSE)
+        msg = mail.EmailMessage('Subject', 'Body', 'from@example.com', to=['not a valid email'])
+        with self.assertRaises(AnymailAPIError):
+            msg.send()
+
+    def test_fail_silently(self):
+        self.set_mock_response(status_code=400, raw=self.INVALID_TO_RESPONSE)
+        sent = mail.send_mail('Subject', 'Body', 'from@example.com', ['not a valid email'],
+                              fail_silently=True)
+        self.assertEqual(sent, 0)
+
+
+@override_settings(ANYMAIL_SEND_DEFAULTS={
+    'metadata': {'global': 'globalvalue', 'other': 'othervalue'},
+    'tags': ['globaltag'],
+    'track_clicks': True,
+    'track_opens': True,
+    'esp_extra': {'o:globaloption': 'globalsetting'},
+})
+class MailgunBackendSendDefaultsTests(MailgunBackendMockAPITestCase):
+    """Tests backend support for global SEND_DEFAULTS"""
+
+    def test_send_defaults(self):
+        """Test that global send defaults are applied"""
+        self.message.send()
+        data = self.get_api_call_data()
+        # All these values came from ANYMAIL_SEND_DEFAULTS:
+        self.assertEqual(data['v:global'], 'globalvalue')
+        self.assertEqual(data['v:other'], 'othervalue')
+        self.assertEqual(data['o:tag'], ['globaltag'])
+        self.assertEqual(data['o:tracking-clicks'], 'yes')
+        self.assertEqual(data['o:tracking-opens'], 'yes')
+        self.assertEqual(data['o:globaloption'], 'globalsetting')
+
+    def test_merge_message_with_send_defaults(self):
+        """Test that individual message settings are *merged into* the global send defaults"""
+        self.message.metadata = {'message': 'messagevalue', 'other': 'override'}
+        self.message.tags = ['messagetag']
+        self.message.track_clicks = False
+        self.message.esp_extra = {'o:messageoption': 'messagesetting'}
+
+        self.message.send()
+        data = self.get_api_call_data()
+        # All these values came from ANYMAIL_SEND_DEFAULTS + message.*:
+        self.assertEqual(data['v:global'], 'globalvalue')
+        self.assertEqual(data['v:message'], 'messagevalue')  # additional metadata
+        self.assertEqual(data['v:other'], 'override')  # override global value
+        self.assertEqual(data['o:tag'], ['globaltag', 'messagetag'])  # tags concatenated
+        self.assertEqual(data['o:tracking-clicks'], 'no')  # message overrides
+        self.assertEqual(data['o:tracking-opens'], 'yes')
+        self.assertEqual(data['o:globaloption'], 'globalsetting')
+        self.assertEqual(data['o:messageoption'], 'messagesetting')  # additional esp_extra
+
+    @override_settings(ANYMAIL_MAILGUN_SEND_DEFAULTS={
+        'tags': ['esptag'],
+        'metadata': {'esp': 'espvalue'},
+        'track_opens': False,
+    })
+    def test_esp_send_defaults(self):
+        """Test that ESP-specific send defaults override individual global defaults"""
+        self.message.send()
+        data = self.get_api_call_data()
+        # All these values came from ANYMAIL_SEND_DEFAULTS plus ANYMAIL_MAILGUN_SEND_DEFAULTS:
+        self.assertNotIn('v:global', data)  # entire metadata overridden
+        self.assertEqual(data['v:esp'], 'espvalue')
+        self.assertEqual(data['o:tag'], ['esptag'])  # entire tags overridden
+        self.assertEqual(data['o:tracking-clicks'], 'yes')  # we didn't override the global track_clicks
+        self.assertEqual(data['o:tracking-opens'], 'no')
+        self.assertEqual(data['o:globaloption'], 'globalsetting')  # we didn't override the global esp_extra
+
+
+@override_settings(EMAIL_BACKEND="anymail.backends.mailgun.MailgunBackend")
+class MailgunBackendImproperlyConfiguredTests(SimpleTestCase, AnymailTestMixin):
+    """Test ESP backend without required settings in place"""
+
+    def test_missing_api_key(self):
+        with self.assertRaises(ImproperlyConfigured) as cm:
+            mail.send_mail('Subject', 'Message', 'from@example.com', ['to@example.com'])
+        errmsg = str(cm.exception)
+        # Make sure the error mentions MAILGUN_API_KEY and ANYMAIL_MAILGUN_API_KEY
+        self.assertRegex(errmsg, r'\bMAILGUN_API_KEY\b')
+        self.assertRegex(errmsg, r'\bANYMAIL_MAILGUN_API_KEY\b')
--- a/anymail/tests/test_mailgun_integration.py
+++ b/anymail/tests/test_mailgun_integration.py
@@ -0,0 +1,165 @@
+from __future__ import unicode_literals
+
+import os
+import unittest
+from datetime import datetime, timedelta
+from time import mktime, sleep
+
+import requests
+from django.test import SimpleTestCase
+from django.test.utils import override_settings
+
+from anymail.exceptions import AnymailAPIError
+from anymail.message import AnymailMessage
+
+from .utils import sample_image_content, AnymailTestMixin
+
+
+MAILGUN_TEST_API_KEY = os.getenv('MAILGUN_TEST_API_KEY')
+MAILGUN_TEST_DOMAIN = os.getenv('MAILGUN_TEST_DOMAIN')
+
+
+@unittest.skipUnless(MAILGUN_TEST_API_KEY and MAILGUN_TEST_DOMAIN,
+                     "Set MAILGUN_TEST_API_KEY and MAILGUN_TEST_DOMAIN environment variables "
+                     "to run Mailgun integration tests")
+@override_settings(ANYMAIL_MAILGUN_API_KEY=MAILGUN_TEST_API_KEY,
+                   ANYMAIL_MAILGUN_SEND_DEFAULTS={
+                       'esp_extra': {'o:testmode': 'yes',
+                                     'sender_domain': MAILGUN_TEST_DOMAIN}},
+                   EMAIL_BACKEND="anymail.backends.mailgun.MailgunBackend")
+class MailgunBackendIntegrationTests(SimpleTestCase, AnymailTestMixin):
+    """Mailgun API integration tests
+
+    These tests run against the **live** Mailgun API, using the
+    environment variable `MAILGUN_TEST_API_KEY` as the API key
+    and `MAILGUN_TEST_DOMAIN` as the sender domain.
+    If those variables are not set, these tests won't run.
+
+    """
+
+    def setUp(self):
+        super(MailgunBackendIntegrationTests, self).setUp()
+        self.message = AnymailMessage('Anymail integration test', 'Text content',
+                                      'from@example.com', ['to@example.com'])
+        self.message.attach_alternative('<p>HTML content</p>', "text/html")
+
+    def fetch_mailgun_events(self, message_id, event=None,
+                             initial_delay=2, retry_delay=1, max_retries=5):
+        """Return list of Mailgun events related to message_id"""
+        url = "https://api.mailgun.net/v3/%s/events" % MAILGUN_TEST_DOMAIN
+        auth = ("api", MAILGUN_TEST_API_KEY)
+
+        # Despite the docs, Mailgun's events API actually expects the message-id
+        # without the <...> brackets (so, not exactly "as returned by the messages API")
+        # https://documentation.mailgun.com/api-events.html#filter-field
+        params = {'message-id': message_id[1:-1]}  # strip <...>
+        if event is not None:
+            params['event'] = event
+
+        # It can take a few seconds for the events to show up
+        # in Mailgun's logs, so retry a few times if necessary:
+        sleep(initial_delay)
+        for retry in range(max_retries):
+            if retry > 0:
+                sleep(retry_delay)
+            response = requests.get(url, auth=auth, params=params)
+            response.raise_for_status()
+            items = response.json()["items"]
+            if len(items) > 0:
+                return items
+        return None
+
+    def test_simple_send(self):
+        # Example of getting the Mailgun 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['to@example.com'].status
+        message_id = anymail_status.recipients['to@example.com'].message_id
+
+        self.assertEqual(sent_status, 'queued')  # Mailgun always queues
+        self.assertGreater(len(message_id), 0)  # don't know what it'll be, but it should exist
+
+        self.assertEqual(anymail_status.status, {sent_status})  # set of all recipient statuses
+        self.assertEqual(anymail_status.message_id, message_id)
+
+    def test_all_options(self):
+        send_at = datetime.now().replace(microsecond=0) + timedelta(minutes=2)
+        send_at_timestamp = mktime(send_at.timetuple())  # python3: send_at.timestamp()
+        message = AnymailMessage(
+            subject="Anymail all-options integration test",
+            body="This is the text body",
+            from_email="Test From <from@example.com>",
+            to=["to1@example.com", "Recipient 2 <to2@example.com>"],
+            cc=["cc1@example.com", "Copy 2 <cc2@example.com>"],
+            bcc=["bcc1@example.com", "Blind Copy 2 <bcc2@example.com>"],
+            reply_to=["reply1@example.com", "Reply 2 <reply2@example.com>"],
+            headers={"X-Anymail-Test": "value"},
+
+            metadata={"meta1": "simple string", "meta2": 2, "meta3": {"complex": "value"}},
+            send_at=send_at,
+            tags=["tag 1", "tag 2"],
+            track_clicks=False,
+            track_opens=True,
+        )
+        message.attach("attachment1.txt", "Here is some\ntext for you", "text/plain")
+        message.attach("attachment2.csv", "ID,Name\n1,3", "text/csv")
+        cid = message.attach_inline_image(sample_image_content(), domain=MAILGUN_TEST_DOMAIN)
+        message.attach_alternative(
+            "<div>This is the <i>html</i> body <img src='cid:%s'></div>" % cid,
+            "text/html")
+
+        message.send()
+        self.assertEqual(message.anymail_status.status, {'queued'})  # Mailgun always queues
+        message_id = message.anymail_status.message_id
+
+        events = self.fetch_mailgun_events(message_id, event="accepted")
+        if events is None:
+            self.skipTest("No Mailgun 'accepted' event after 30sec -- can't complete this test")
+            return
+
+        event = events.pop()
+        self.assertCountEqual(event["tags"], ["tag 1", "tag 2"])  # don't care about order
+        self.assertEqual(event["user-variables"],
+                         {"meta1": "simple string",
+                          "meta2": "2",  # numbers become strings
+                          "meta3": '{"complex": "value"}'})  # complex values become json
+
+        self.assertEqual(event["message"]["scheduled-for"], send_at_timestamp)
+        self.assertCountEqual(event["message"]["recipients"],
+                              ['to1@example.com', 'to2@example.com', 'cc1@example.com', 'cc2@example.com',
+                               'bcc1@example.com', 'bcc2@example.com'])  # don't care about order
+
+        headers = event["message"]["headers"]
+        self.assertEqual(headers["from"], "Test From <from@example.com>")
+        self.assertEqual(headers["to"], "to1@example.com, Recipient 2 <to2@example.com>")
+        self.assertEqual(headers["subject"], "Anymail all-options integration test")
+
+        attachments = event["message"]["attachments"]
+        self.assertEqual(len(attachments), 2)  # because inline image shouldn't be an attachment
+        self.assertEqual(attachments[0]["filename"], "attachment1.txt")
+        self.assertEqual(attachments[0]["content-type"], "text/plain")
+        self.assertEqual(attachments[1]["filename"], "attachment2.csv")
+        self.assertEqual(attachments[1]["content-type"], "text/csv")
+
+        # No other fields are verifiable from the event data.
+        # (We could try fetching the message from event["storage"]["url"]
+        # to verify content and other headers.)
+
+    def test_invalid_from(self):
+        self.message.from_email = 'webmaster'
+        with self.assertRaises(AnymailAPIError) as cm:
+            self.message.send()
+        err = cm.exception
+        self.assertEqual(err.status_code, 400)
+        self.assertIn("'from' parameter is not a valid address", str(err))
+
+    @override_settings(ANYMAIL_MAILGUN_API_KEY="Hey, that's not an API key!")
+    def test_invalid_api_key(self):
+        with self.assertRaises(AnymailAPIError) as cm:
+            self.message.send()
+        err = cm.exception
+        self.assertEqual(err.status_code, 401)
+        # Mailgun doesn't offer any additional explanation in its response body
+        # self.assertIn("Forbidden", str(err))
--- a/anymail/tests/test_mandrill_send.py
+++ b/anymail/tests/test_mandrill_send.py
@@ -4,7 +4,6 @@ from __future__ import unicode_literals

 import json
 import os
-import re
 import six
 import unittest
 from base64 import b64decode
@@ -15,13 +14,13 @@ from email.mime.image import MIMEImage

 from django.core import mail
 from django.core.exceptions import ImproperlyConfigured
-from django.core.mail import make_msgid
 from django.test import TestCase
 from django.test.utils import override_settings
 from django.utils.timezone import get_fixed_timezone, override as override_current_timezone

 from anymail.exceptions import (AnymailAPIError, AnymailRecipientsRefused,
                                AnymailSerializationError, AnymailUnsupportedFeature)
+from anymail.message import attach_inline_image

 from .mock_backend import DjrillBackendMockAPITestCase

@@ -224,18 +223,14 @@ class DjrillBackendTests(DjrillBackendMockAPITestCase):
        self.assertEqual(len(attachments), 1)

    def test_embedded_images(self):
-        image_data = self.sample_image_content()  # Read from a png file
-        image_cid = make_msgid("img")  # Content ID per RFC 2045 section 7 (with <...>)
-        image_cid_no_brackets = image_cid[1:-1]  # Without <...>, for use as the <img> tag src
-
        text_content = 'This has an inline image.'
-        html_content = '<p>This has an <img src="cid:%s" alt="inline" /> image.</p>' % image_cid_no_brackets
        email = mail.EmailMultiAlternatives('Subject', text_content, 'from@example.com', ['to@example.com'])
-        email.attach_alternative(html_content, "text/html")

-        image = MIMEImage(image_data)
-        image.add_header('Content-ID', image_cid)
-        email.attach(image)
+        image_data = self.sample_image_content()  # Read from a png file
+        cid = attach_inline_image(email, image_data)
+
+        html_content = '<p>This has an <img src="cid:%s" alt="inline" /> image.</p>' % cid
+        email.attach_alternative(html_content, "text/html")

        email.send()
        data = self.get_api_call_data()
@@ -243,7 +238,7 @@ class DjrillBackendTests(DjrillBackendMockAPITestCase):
        self.assertEqual(data['message']['html'], html_content)
        self.assertEqual(len(data['message']['images']), 1)
        self.assertEqual(data['message']['images'][0]["type"], "image/png")
-        self.assertEqual(data['message']['images'][0]["name"], image_cid)
+        self.assertEqual(data['message']['images'][0]["name"], cid)
        self.assertEqual(decode_att(data['message']['images'][0]["content"]), image_data)
        # Make sure neither the html nor the inline image is treated as an attachment:
        self.assertFalse('attachments' in data['message'])
@@ -342,9 +337,6 @@ class DjrillMandrillFeatureTests(DjrillBackendMockAPITestCase):
        self.message = mail.EmailMessage('Subject', 'Text Body',
            'from@example.com', ['to@example.com'])

-    def assertStrContains(self, haystack, needle, msg=None):
-        six.assertRegex(self, haystack, re.escape(needle), msg)
-
    def test_tracking(self):
        # First make sure we're not setting the API param if the track_click
        # attr isn't there. (The Mandrill account option of True for html,
@@ -570,8 +562,8 @@ class DjrillMandrillFeatureTests(DjrillBackendMockAPITestCase):
            self.message.send()
        err = cm.exception
        self.assertTrue(isinstance(err, TypeError))  # Djrill 1.x re-raised TypeError from json.dumps
-        self.assertStrContains(str(err), "Don't know how to send this data to Mandrill")  # our added context
-        self.assertStrContains(str(err), "Decimal('19.99') is not JSON serializable")  # original message
+        self.assertIn("Don't know how to send this data to Mandrill", str(err))  # our added context
+        self.assertIn("Decimal('19.99') is not JSON serializable", str(err))  # original message

    def test_dates_not_serialized(self):
        """Pre-2.0 Djrill accidentally serialized dates to ISO"""
--- a/anymail/tests/utils.py
+++ b/anymail/tests/utils.py
@@ -0,0 +1,47 @@
+# Anymail test utils
+import os
+import unittest
+from base64 import b64decode
+
+import six
+
+
+def decode_att(att):
+    """Returns the original data from base64-encoded attachment content"""
+    return b64decode(att.encode('ascii'))
+
+
+SAMPLE_IMAGE_FILENAME = "sample_image.png"
+
+
+def sample_image_path(filename=SAMPLE_IMAGE_FILENAME):
+    """Returns path to an actual image file in the tests directory"""
+    test_dir = os.path.dirname(os.path.abspath(__file__))
+    path = os.path.join(test_dir, filename)
+    return path
+
+
+def sample_image_content(filename=SAMPLE_IMAGE_FILENAME):
+    """Returns contents of an actual image file from the tests directory"""
+    filename = sample_image_path(filename)
+    with open(filename, "rb") as f:
+        return f.read()
+
+
+class AnymailTestMixin:
+    """Helpful additional methods for Anymail tests"""
+
+    pass
+    # Plus these methods added below:
+    # assertCountEqual
+    # assertRaisesRegex
+    # assertRegex
+
+# Add the Python 3 TestCase assertions, if they're not already there.
+# (The six implementations cause infinite recursion if installed on
+# a py3 TestCase.)
+for method in ('assertCountEqual', 'assertRaisesRegex', 'assertRegex'):
+    try:
+        getattr(unittest.TestCase, method)
+    except AttributeError:
+        setattr(AnymailTestMixin, method, getattr(six, method))
--- a/anymail/utils.py
+++ b/anymail/utils.py
@@ -1,7 +1,8 @@
 import mimetypes
 from base64 import b64encode
+from calendar import timegm
 from email.mime.base import MIMEBase
-from email.utils import parseaddr
+from email.utils import parseaddr, formatdate

 import six
 from django.conf import settings
@@ -41,7 +42,7 @@ def combine(*args):
                try:
                    result.update(value)  # shallow merge if dict-like
                except AttributeError:
-                    result += value  # concatenate if sequence-like
+                    result = result + value  # concatenate if sequence-like
    return result


@@ -97,10 +98,11 @@ class Attachment(object):
    """A normalized EmailMessage.attachments item with additional functionality

    Normalized to have these properties:
-    name: attachment filename; may be empty string; will be Content-ID for inline attachments
+    name: attachment filename; may be empty string; will be Content-ID (without <>) for inline attachments
    content
    mimetype: the content type; guessed if not explicit
    inline: bool, True if attachment has a Content-ID header
+    content_id: for inline, the Content-ID (with <>)
    """

    def __init__(self, attachment, encoding):
@@ -109,6 +111,7 @@ class Attachment(object):
        self._attachment = attachment
        self.encoding = encoding  # should we be checking attachment["Content-Encoding"] ???
        self.inline = False
+        self.content_id = None

        if isinstance(attachment, MIMEBase):
            self.name = attachment.get_filename()
@@ -117,7 +120,8 @@ class Attachment(object):
            # Treat image attachments that have content ids as inline:
            if attachment.get_content_maintype() == "image" and attachment["Content-ID"] is not None:
                self.inline = True
-                self.name = attachment["Content-ID"]
+                self.content_id = attachment["Content-ID"]  # including the <...>
+                self.name = self.content_id[1:-1]  # without the <, >
        else:
            (self.name, self.content, self.mimetype) = attachment

@@ -175,3 +179,11 @@ def get_anymail_setting(setting, default=UNSET, allow_bare=False):
                raise ImproperlyConfigured(message)
            else:
                return default
+
+
+def rfc2822date(dt):
+    """Turn an aware datetime into a date string as specified in RFC 2822."""
+    # This is the equivalent of Python 3.3's email.utils.format_datetime
+    assert dt.tzinfo is not None  # only aware datetimes allowed
+    timeval = timegm(dt.utctimetuple())
+    return formatdate(timeval, usegmt=True)
--- a/setup.py
+++ b/setup.py
@@ -31,10 +31,14 @@ setup(
    license="BSD License",
    packages=["anymail"],
    zip_safe=False,
-    install_requires=["requests>=1.0.0", "django>=1.4"],
+    install_requires=["django>=1.8", "six"],
+    extras_require={
+        "mailgun": ["requests>=2.4.3"],
+        "mandrill": ["requests>=1.0.0"],
+    },
    include_package_data=True,
    test_suite="runtests.runtests",
-    tests_require=["mock", "six"],
+    tests_require=["mock"],
    classifiers=[
        "Development Status :: 2 - Pre-Alpha",
        "Programming Language :: Python",