Add support for Reply-To.

sgbackend/mail.py

@@ -101,11 +101,31 @@ def _build_sg_mail(self, email):
         if hasattr(email, 'template_id'):
             mail.set_template_id(email.template_id)
             if hasattr(email, 'substitutions'):
-                for k, v in email.substitutions.items():
-                    personalization.add_substitution(Substitution(k, v))
-
-        for k, v in email.extra_headers.items():
-            mail.add_header({k: v})
+                for key, value in email.substitutions.items():
+                    personalization.add_substitution(Substitution(key, value))
+
+        # SendGrid does not support adding Reply-To as an extra
+        # header, so it needs to be manually removed if it exists.
+        reply_to_string = ""
+        for key, value in email.extra_headers.items():
+            if key.lower() == "reply-to":
+                reply_to_string = value
+            else:
+                mail.add_header({key: value})
+        # Note that if you set a "Reply-To" header *and* the reply_to
+        # attribute, the header's value will be used.
+        if not mail.reply_to and hasattr(email, "reply_to") and email.reply_to:
+            # SendGrid only supports setting Reply-To to a single address.
+            # See https://github.com/sendgrid/sendgrid-csharp/issues/339.
+            reply_to_string = email.reply_to[0]
+        # Determine whether reply_to contains a name and email address, or
+        # just an email address.
+        if reply_to_string:
+            reply_to_name, reply_to_email = rfc822.parseaddr(reply_to_string)
+            if reply_to_name and reply_to_email:
+                mail.set_reply_to(Email(reply_to_email, reply_to_name))
+            elif reply_to_email:
+                mail.set_reply_to(Email(reply_to_email))
 
         for attachment in email.attachments:
             if isinstance(attachment, MIMEBase):

tests/test_mail.py

@@ -69,6 +69,45 @@ def test_build_w_bcc_sg_email(self):
                  'from': {'email': 'webmaster@localhost'}, 'subject': ''}
             )
 
+    def test_build_w_reply_to_sg_email(self):
+        # Test setting a Reply-To header.
+        msg = EmailMessage()
+        msg.extra_headers = {'Reply-To': 'andrii.soldatenko@test.com'}
+        with self.settings(SENDGRID_API_KEY='test_key'):
+            mail = SendGridBackend()._build_sg_mail(msg)
+            self.assertEqual(
+                mail,
+                {'content': [{'value': '', 'type': 'text/plain'}],
+                 'personalizations': [{'subject': ''}],
+                 'reply_to': {'email': 'andrii.soldatenko@test.com'},
+                 'from': {'email': 'webmaster@localhost'}, 'subject': ''}
+            )
+        # Test using the reply_to attribute.
+        msg = EmailMessage(reply_to=('andrii.soldatenko@test.com',))
+        with self.settings(SENDGRID_API_KEY='test_key'):
+            mail = SendGridBackend()._build_sg_mail(msg)
+            self.assertEqual(
+                mail,
+                {'content': [{'value': '', 'type': 'text/plain'}],
+                 'personalizations': [{'subject': ''}],
+                 'reply_to': {'email': 'andrii.soldatenko@test.com'},
+                 'from': {'email': 'webmaster@localhost'}, 'subject': ''}
+            )
+        # Test using "name <email>" format.
+        msg = EmailMessage(
+            reply_to=('Andrii Soldatenko <andrii.soldatenko@test.com>',))
+        with self.settings(SENDGRID_API_KEY='test_key'):
+            mail = SendGridBackend()._build_sg_mail(msg)
+            self.assertEqual(
+                mail,
+                {'content': [{'value': '', 'type': 'text/plain'}],
+                 'personalizations': [{'subject': ''}],
+                 'reply_to': {
+                    'name': 'Andrii Soldatenko',
+                    'email': 'andrii.soldatenko@test.com'},
+                 'from': {'email': 'webmaster@localhost'}, 'subject': ''}
+            )
+
     def test_build_empty_multi_alternatives_sg_email(self):
         html_content = '<p>This is an <strong>important</strong> message.</p>'
         msg = EmailMultiAlternatives()