diff --git a/anymail/backends/base.py b/anymail/backends/base.py
new file mode 100644
index 0000000..455f051
--- /dev/null
+++ b/anymail/backends/base.py
@@ -0,0 +1,248 @@
+import json
+import requests
+
+from django.core.mail.backends.base import BaseEmailBackend
+
+from .._version import __version__
+from ..exceptions import AnymailError, AnymailRequestsAPIError, AnymailSerializationError, AnymailImproperlyConfigured
+
+
+class AnymailBaseBackend(BaseEmailBackend):
+    """
+    Base Anymail email backend
+    """
+
+    def open(self):
+        """
+        Open and persist a connection to the ESP's API, and whether
+        a new connection was created.
+
+        Callers must ensure they later call close, if (and only if) open
+        returns True.
+        """
+        # Subclasses should use an instance property to maintain a cached
+        # connection, and return True iff they initialize that instance
+        # property in _this_ open call. (If the cached connection already
+        # exists, just do nothing and return False.)
+        #
+        # Subclasses should swallow operational errors if self.fail_silently
+        # (e.g., network errors), but otherwise can raise any errors.
+        #
+        # (Returning a bool to indicate whether connection was created is
+        # borrowed from django.core.email.backends.SMTPBackend)
+        return False
+
+    def close(self):
+        """
+        Close the cached connection created by open.
+
+        You must only call close if your code called open and it returned True.
+        """
+        # Subclasses should tear down the cached connection and clear
+        # the instance property.
+        #
+        # Subclasses should swallow operational errors if self.fail_silently
+        # (e.g., network errors), but otherwise can raise any errors.
+        pass
+
+    def send_messages(self, email_messages):
+        """
+        Sends one or more EmailMessage objects and returns the number of email
+        messages sent.
+        """
+        # This API is specified by Django's core BaseEmailBackend
+        # (so you can't change it to, e.g., return detailed status).
+        # Subclasses shouldn't need to override.
+
+        num_sent = 0
+        if not email_messages:
+            return num_sent
+
+        created_session = self.open()
+
+        try:
+            for message in email_messages:
+                try:
+                    sent = self._send(message)
+                except AnymailError:
+                    if self.fail_silently:
+                        sent = False
+                    else:
+                        raise
+                if sent:
+                    num_sent += 1
+        finally:
+            if created_session:
+                self.close()
+
+        return num_sent
+
+    def _send(self, message):
+        """Sends the EmailMessage message, and returns True if the message was sent.
+
+        This should only be called by the base send_messages loop.
+
+        Implementations must raise exceptions derived from AnymailError for
+        anticipated failures that should be suppressed in fail_silently mode.
+        """
+        message.anymail_status = None
+        esp_response_attr = "%s_response" % self.esp_name.lower()  # e.g., message.mandrill_response
+        setattr(message, esp_response_attr, None)  # until we have a response
+        if not message.recipients():
+            return False
+
+        payload = self.build_message_payload(message)
+        # FUTURE: if pre-send-signal OK...
+        response = self.post_to_esp(payload, message)
+
+        parsed_response = self.deserialize_response(response, payload, message)
+        setattr(message, esp_response_attr, parsed_response)
+        message.anymail_status = self.validate_response(parsed_response, response, payload, message)
+        # FUTURE: post-send signal
+
+        return True
+
+    def build_message_payload(self, message):
+        """Return a payload with all message-specific options for ESP send call.
+
+        message is an EmailMessage, possibly with additional Anymail-specific attrs
+
+        Can raise AnymailUnsupportedFeature for unsupported options in message.
+        """
+        raise NotImplementedError("%s.%s must implement build_message_payload" %
+                                  (self.__class__.__module__, self.__class__.__name__))
+
+    def post_to_esp(self, payload, message):
+        """Post payload to ESP send API endpoint, and return the raw response.
+
+        payload is the result of build_message_payload
+        message is the original EmailMessage
+        return should be a raw response
+
+        Can raise AnymailAPIError (or derived exception) for problems posting to the ESP
+        """
+        raise NotImplementedError("%s.%s must implement build_message_payload" %
+                                  (self.__class__.__module__, self.__class__.__name__))
+
+    def deserialize_response(self, response, payload, message):
+        """Deserialize a raw ESP response
+
+        Can raise AnymailAPIError (or derived exception) if response is unparsable
+        """
+        raise NotImplementedError("%s.%s must implement build_message_payload" %
+                                  (self.__class__.__module__, self.__class__.__name__))
+
+    def validate_response(self, parsed_response, response, payload, message):
+        """Validate parsed_response, raising exceptions for any problems, and return normalized status.
+
+        Extend this to provide your own validation checks.
+        Validation exceptions should inherit from anymail.exceptions.AnymailError
+        for proper fail_silently behavior.
+
+        If *all* recipients are refused or invalid, should raise AnymailRecipientsRefused
+
+        Returns one of "sent", "queued", "refused", "error" or "multi"
+        """
+        raise NotImplementedError("%s.%s must implement validate_response" %
+                                  (self.__class__.__module__, self.__class__.__name__))
+
+    @property
+    def esp_name(self):
+        """
+        Read-only name of the ESP for this backend.
+
+        (E.g., MailgunBackend will return "Mailgun")
+        """
+        return self.__class__.__name__.replace("Backend", "")
+
+
+class AnymailRequestsBackend(AnymailBaseBackend):
+    """
+    Base Anymail email backend for ESPs that use an HTTP API via requests
+    """
+
+    def __init__(self, api_url, **kwargs):
+        """Init options from Django settings"""
+        self.api_url = api_url
+        super(AnymailRequestsBackend, self).__init__(**kwargs)
+        self.session = None
+
+    def open(self):
+        if self.session:
+            return False  # already exists
+
+        try:
+            self.session = requests.Session()
+        except requests.RequestException:
+            if not self.fail_silently:
+                raise
+        else:
+            self.session.headers["User-Agent"] = "Anymail/%s %s" % (
+                __version__, self.session.headers.get("User-Agent", ""))
+            return True
+
+    def close(self):
+        if self.session is None:
+            return
+        try:
+            self.session.close()
+        except requests.RequestException:
+            if not self.fail_silently:
+                raise
+        finally:
+            self.session = None
+
+    def _send(self, message):
+        if self.session is None:
+            class_name = self.__class__.__name__
+            raise RuntimeError(
+                "Session has not been opened in {class_name}._send. "
+                "(This is either an implementation error in {class_name}, "
+                "or you are incorrectly calling _send directly.)".format(class_name=class_name))
+        return super(AnymailRequestsBackend, self)._send(message)
+
+    def get_api_url(self, payload, message):
+        """Return the correct ESP url for sending payload
+
+        Override this to substitute your own logic for determining API endpoint.
+        """
+        return self.api_url
+
+    def serialize_payload(self, payload, message):
+        """Return payload serialized to post data.
+
+        Should raise AnymailSerializationError if payload is not serializable
+        """
+        try:
+            return json.dumps(payload)
+        except TypeError as err:
+            # Add some context to the "not JSON serializable" message
+            raise AnymailSerializationError(orig_err=err, email_message=message, payload=payload)
+
+    def post_to_esp(self, payload, message):
+        """Post payload to ESP send API endpoint, and return the raw response.
+
+        payload is the result of build_message_payload
+        message is the original EmailMessage
+        return should be a requests.Response
+
+        Can raise AnymailRequestsAPIError for HTTP errors in the post
+        """
+        api_url = self.get_api_url(payload, message)
+        post_data = self.serialize_payload(payload, message)
+
+        response = self.session.post(api_url, data=post_data)
+        if response.status_code != 200:
+            raise AnymailRequestsAPIError(email_message=message, payload=payload, response=response)
+        return response
+
+    def deserialize_response(self, response, payload, message):
+        """Return parsed ESP API response
+
+        Can raise AnymailRequestsAPIError if response is unparsable
+        """
+        try:
+            return response.json()
+        except ValueError:
+            raise AnymailRequestsAPIError("Invalid JSON in %s API response" % self.esp_name,
+                                          email_message=message, payload=payload, response=response)
diff --git a/anymail/backends/mandrill.py b/anymail/backends/mandrill.py
index e537406..9cf1b69 100644
--- a/anymail/backends/mandrill.py
+++ b/anymail/backends/mandrill.py
@@ -1,6 +1,4 @@
-import json
 import mimetypes
-import requests
 from base64 import b64encode
 from datetime import date, datetime
 from email.mime.base import MIMEBase
@@ -11,32 +9,32 @@ except ImportError:
     from urllib.parse import urljoin  # python 3
 
 from django.conf import settings
-from django.core.exceptions import ImproperlyConfigured
-from django.core.mail.backends.base import BaseEmailBackend
 from django.core.mail.message import sanitize_address, DEFAULT_ATTACHMENT_MIME_TYPE
 
-from .._version import __version__
-from ..exceptions import (AnymailError, AnymailRequestsAPIError, AnymailRecipientsRefused,
-                          AnymailSerializationError, AnymailUnsupportedFeature)
+from ..exceptions import (AnymailImproperlyConfigured,
+                          AnymailRequestsAPIError, AnymailRecipientsRefused,
+                          AnymailUnsupportedFeature)
+
+from .base import AnymailRequestsBackend
 
 
-class MandrillBackend(BaseEmailBackend):
+class MandrillBackend(AnymailRequestsBackend):
     """
     Mandrill API Email Backend
     """
 
     def __init__(self, **kwargs):
         """Init options from Django settings"""
-        super(MandrillBackend, self).__init__(**kwargs)
+        api_url = getattr(settings, "MANDRILL_API_URL", "https://mandrillapp.com/api/1.0")
+        if not api_url.endswith("/"):
+            api_url += "/"
+
+        super(MandrillBackend, self).__init__(api_url, **kwargs)
 
         try:
             self.api_key = settings.MANDRILL_API_KEY
         except AttributeError:
-            raise ImproperlyConfigured("Set MANDRILL_API_KEY in settings.py to use Djrill")
-
-        self.api_url = getattr(settings, "MANDRILL_API_URL", "https://mandrillapp.com/api/1.0")
-        if not self.api_url.endswith("/"):
-            self.api_url += "/"
+            raise AnymailImproperlyConfigured("Set MANDRILL_API_KEY in settings.py to use Anymail Mandrill backend")
 
         self.global_settings = {}
         try:
@@ -44,7 +42,7 @@ class MandrillBackend(BaseEmailBackend):
         except AttributeError:
             pass  # no MANDRILL_SETTINGS setting
         except (TypeError, ValueError):  # e.g., not enumerable
-            raise ImproperlyConfigured("MANDRILL_SETTINGS must be a dict or mapping")
+            raise AnymailImproperlyConfigured("MANDRILL_SETTINGS must be a dict or mapping")
 
         try:
             self.global_settings["subaccount"] = settings.MANDRILL_SUBACCOUNT
@@ -54,100 +52,7 @@ class MandrillBackend(BaseEmailBackend):
         self.ignore_recipient_status = getattr(settings, "MANDRILL_IGNORE_RECIPIENT_STATUS", False)
         self.session = None
 
-    def open(self):
-        """
-        Ensure we have a requests Session to connect to the Mandrill API.
-        Returns True if a new session was created (and the caller must close it).
-        """
-        if self.session:
-            return False  # already exists
-
-        try:
-            self.session = requests.Session()
-        except requests.RequestException:
-            if not self.fail_silently:
-                raise
-        else:
-            self.session.headers["User-Agent"] = "Djrill/%s %s" % (
-                __version__, self.session.headers.get("User-Agent", ""))
-            return True
-
-    def close(self):
-        """
-        Close the Mandrill API Session unconditionally.
-
-        (You should call this only if you called open and it returned True;
-        else someone else created the session and will clean it up themselves.)
-        """
-        if self.session is None:
-            return
-        try:
-            self.session.close()
-        except requests.RequestException:
-            if not self.fail_silently:
-                raise
-        finally:
-            self.session = None
-
-    def send_messages(self, email_messages):
-        """
-        Sends one or more EmailMessage objects and returns the number of email
-        messages sent.
-        """
-        if not email_messages:
-            return 0
-
-        created_session = self.open()
-        if not self.session:
-            return 0  # exception in self.open with fail_silently
-
-        num_sent = 0
-        try:
-            for message in email_messages:
-                sent = self._send(message)
-                if sent:
-                    num_sent += 1
-        finally:
-            if created_session:
-                self.close()
-
-        return num_sent
-
-    def _send(self, message):
-        message.mandrill_response = None  # until we have a response
-        if not message.recipients():
-            return False
-
-        try:
-            payload = self.get_base_payload()
-            self.build_send_payload(payload, message)
-            response = self.post_to_mandrill(payload, message)
-
-            # add the response from mandrill to the EmailMessage so callers can inspect it
-            message.mandrill_response = self.parse_response(response, payload, message)
-            self.validate_response(message.mandrill_response, response, payload, message)
-
-        except AnymailError:
-            # every *expected* error is derived from AnymailError;
-            # we deliberately don't silence unexpected errors
-            if not self.fail_silently:
-                raise
-            return False
-
-        return True
-
-    def get_base_payload(self):
-        """Return non-message-dependent payload for Mandrill send call
-
-        (The return value will be modified for the send, so must be a copy
-        of any shared state.)
-        """
-        payload = {
-            "key": self.api_key,
-        }
-        return payload
-
-    def build_send_payload(self, payload, message):
+    def build_message_payload(self, message):
         """Modify payload to add all message-specific options for Mandrill send call.
 
         payload is a dict that will become the Mandrill send data
@@ -160,12 +65,17 @@ class MandrillBackend(BaseEmailBackend):
         if getattr(message, 'alternatives', None):
             self._add_alternatives(message, msg_dict)
         self._add_attachments(message, msg_dict)
-        payload.setdefault('message', {}).update(msg_dict)
+
+        payload = {
+            "key": self.api_key,
+            "message": msg_dict,
+        }
         if hasattr(message, 'template_name'):
             payload['template_name'] = message.template_name
             payload['template_content'] = \
                 self._expand_merge_vars(getattr(message, 'template_content', {}))
         self._add_mandrill_toplevel_options(message, payload)
+        return payload
 
     def get_api_url(self, payload, message):
         """Return the correct Mandrill API url for sending payload
@@ -178,67 +88,28 @@ class MandrillBackend(BaseEmailBackend):
             api_method = "messages/send.json"
         return urljoin(self.api_url, api_method)
 
-    def serialize_payload(self, payload, message):
-        """Return payload serialized to a json str.
-
-        Override this to substitute your own JSON serializer (e.g., to handle dates)
-        """
-        return json.dumps(payload)
-
-    def post_to_mandrill(self, payload, message):
-        """Post payload to correct Mandrill send API endpoint, and return the response.
-
-        payload is a dict to use as Mandrill send data
-        message is the original EmailMessage
-        return should be a requests.Response
-
-        Can raise AnymailSerializationError if payload is not serializable
-        Can raise AnymailRequestsAPIError for HTTP errors in the post
-        """
-        api_url = self.get_api_url(payload, message)
-        try:
-            json_payload = self.serialize_payload(payload, message)
-        except TypeError as err:
-            # Add some context to the "not JSON serializable" message
-            raise AnymailSerializationError(
-                orig_err=err, email_message=message, payload=payload)
-
-        response = self.session.post(api_url, data=json_payload)
-        if response.status_code != 200:
-            raise AnymailRequestsAPIError(email_message=message, payload=payload, response=response)
-        return response
-
-    def parse_response(self, response, payload, message):
-        """Return parsed json from Mandrill API response
-
-        Can raise AnymailRequestsAPIError if response is not valid JSON
-        """
-        try:
-            return response.json()
-        except ValueError:
-            raise AnymailRequestsAPIError("Invalid JSON in Mandrill API response",
-                                          email_message=message, payload=payload, response=response)
-
     def validate_response(self, parsed_response, response, payload, message):
         """Validate parsed_response, raising exceptions for any problems.
-
-        Extend this to provide your own validation checks.
-        Validation exceptions should inherit from anymail.exceptions.DjrillException
-        for proper fail_silently behavior.
-
-        The base version here checks for invalid or refused recipients.
         """
-        if self.ignore_recipient_status:
-            return
         try:
-            recipient_status = [item["status"] for item in parsed_response]
+            unique_statuses = set([item["status"] for item in parsed_response])
         except (KeyError, TypeError):
             raise AnymailRequestsAPIError("Invalid Mandrill API response format",
                                           email_message=message, payload=payload, response=response)
-        # Error if *all* recipients are invalid or refused
-        # (This behavior parallels smtplib.SMTPRecipientsRefused from Django's SMTP EmailBackend)
-        if all([status in ('invalid', 'rejected') for status in recipient_status]):
-            raise AnymailRecipientsRefused(email_message=message, payload=payload, response=response)
+
+        if unique_statuses == {"sent"}:
+            return "sent"
+        elif unique_statuses == {"queued"}:
+            return "queued"
+        elif unique_statuses.issubset({"invalid", "rejected"}):
+            if self.ignore_recipient_status:
+                return "refused"
+            else:
+                # Error if *all* recipients are invalid or refused
+                # (This behavior parallels smtplib.SMTPRecipientsRefused from Django's SMTP EmailBackend)
+                raise AnymailRecipientsRefused(email_message=message, payload=payload, response=response)
+        else:
+            return "multi"
 
     #
     # Payload construction
diff --git a/anymail/exceptions.py b/anymail/exceptions.py
index 70e2300..7a41cb5 100644
--- a/anymail/exceptions.py
+++ b/anymail/exceptions.py
@@ -1,3 +1,4 @@
+from django.core.exceptions import ImproperlyConfigured
 import json
 from requests import HTTPError
 
@@ -67,6 +68,10 @@ class AnymailError(Exception):
         return description
 
 
+class AnymailImproperlyConfigured(AnymailError, ImproperlyConfigured):
+    """Exception for configuration problems"""
+
+
 class AnymailAPIError(AnymailError):
     """Exception for unsuccessful response from ESP's API."""
 
diff --git a/anymail/tests/test_mandrill_send.py b/anymail/tests/test_mandrill_send.py
index 283bd11..5707c77 100644
--- a/anymail/tests/test_mandrill_send.py
+++ b/anymail/tests/test_mandrill_send.py
@@ -525,7 +525,10 @@ class DjrillMandrillFeatureTests(DjrillBackendMockAPITestCase):
         msg = mail.EmailMessage('Subject', 'Message', 'from@example.com', ['to1@example.com'],)
         sent = msg.send()
         self.assertEqual(sent, 1)
+        # noinspection PyUnresolvedReferences
         self.assertEqual(msg.mandrill_response, response)
+        # noinspection PyUnresolvedReferences
+        self.assertEqual(msg.anymail_status, "sent")
 
     def test_send_failed_mandrill_response(self):
         """ If the send fails, mandrill_response should be set to None """
@@ -533,7 +536,10 @@ class DjrillMandrillFeatureTests(DjrillBackendMockAPITestCase):
         msg = mail.EmailMessage('Subject', 'Message', 'from@example.com', ['to1@example.com'],)
         sent = msg.send(fail_silently=True)
         self.assertEqual(sent, 0)
+        # noinspection PyUnresolvedReferences
         self.assertIsNone(msg.mandrill_response)
+        # noinspection PyUnresolvedReferences
+        self.assertIsNone(msg.anymail_status)
 
     def test_send_unparsable_mandrill_response(self):
         """If the send succeeds, but a non-JSON API response, should raise an API exception"""
@@ -541,7 +547,10 @@ class DjrillMandrillFeatureTests(DjrillBackendMockAPITestCase):
         msg = mail.EmailMessage('Subject', 'Message', 'from@example.com', ['to1@example.com'],)
         with self.assertRaises(AnymailAPIError):
             msg.send()
+        # noinspection PyUnresolvedReferences
         self.assertIsNone(msg.mandrill_response)
+        # noinspection PyUnresolvedReferences
+        self.assertIsNone(msg.anymail_status)
 
     def test_json_serialization_errors(self):
         """Try to provide more information about non-json-serializable data"""