Fixed #36309 -- Made email alternatives and attachments pickleable.

Regression in aba0e541caaa086f183197eaaca0ac20a730bbe4 and in
d5bebc1c26d4c0ec9eaa057aefc5b38649c0ba3b.

Thanks Florent Messa for the report, and Jake Howard and Claude
Paroz for the review.

django/core/mail/message.py

@@ -191,8 +191,8 @@ class SafeMIMEMultipart(MIMEMixin, MIMEMultipart):
         MIMEMultipart.__setitem__(self, name, val)
 
 
-EmailAlternative = namedtuple("Alternative", ["content", "mimetype"])
+EmailAlternative = namedtuple("EmailAlternative", ["content", "mimetype"])
-EmailAttachment = namedtuple("Attachment", ["filename", "content", "mimetype"])
+EmailAttachment = namedtuple("EmailAttachment", ["filename", "content", "mimetype"])
 
 
 class EmailMessage:

docs/releases/5.2.1.txt

@@ -48,3 +48,6 @@ Bugfixes
 * Fixed a regression in Django 5.2, introduced when fixing :cve:`2025-26699`,
   where the :tfilter:`wordwrap` template filter did not preserve empty lines
   between paragraphs after wrapping text (:ticket:`36341`).
+
+* Fixed a regression in Django 5.2 that caused a crash when serializing email
+  alternatives or attachments due to named tuple mismatches (:ticket:`36309`).

tests/mail/tests.py

@@ -1,5 +1,6 @@
 import mimetypes
 import os
+import pickle
 import shutil
 import socket
 import sys
@@ -654,6 +655,23 @@ class MailTests(MailTestsMixin, SimpleTestCase):
 
         self.assertIn(html_content, msg.message().as_string())
 
+    def test_alternatives_and_attachment_serializable(self):
+        html_content = "<p>This is <strong>html</strong></p>"
+        mime_type = "text/html"
+
+        msg = EmailMultiAlternatives(alternatives=[(html_content, mime_type)])
+        msg.attach("test.txt", "This is plain text.", "plain/text")
+
+        # Alternatives and attachments can be serialized.
+        restored = pickle.loads(pickle.dumps(msg))
+
+        self.assertEqual(restored.subject, msg.subject)
+        self.assertEqual(restored.body, msg.body)
+        self.assertEqual(restored.from_email, msg.from_email)
+        self.assertEqual(restored.to, msg.to)
+        self.assertEqual(restored.alternatives, msg.alternatives)
+        self.assertEqual(restored.attachments, msg.attachments)
+
     def test_none_body(self):
         msg = EmailMessage("subject", None, "from@example.com", ["to@example.com"])
         self.assertEqual(msg.body, "")