diff --git a/tools/linter_lib/custom_check.py b/tools/linter_lib/custom_check.py
index 31e6f2ebe2..bb47667651 100644
--- a/tools/linter_lib/custom_check.py
+++ b/tools/linter_lib/custom_check.py
@@ -227,6 +227,10 @@ python_rules = RuleList(
              'zerver/lib/',
              'zerver/tests/',
              'zerver/views/'])},
+        {'pattern': 'msgid|MSGID',
+         'exclude': set(['tools/check-capitalization',
+                         'tools/i18n/tagmessages']),
+         'description': 'Avoid using "msgid" as a variable name; use "message_id" instead.'},
         {'pattern': '^(?!#)@login_required',
          'description': '@login_required is unsupported; use @zulip_login_required',
          'good_lines': ['@zulip_login_required', '# foo @login_required'],
diff --git a/zerver/management/commands/email_mirror.py b/zerver/management/commands/email_mirror.py
index b6f9f153b6..2a1afaceb6 100644
--- a/zerver/management/commands/email_mirror.py
+++ b/zerver/management/commands/email_mirror.py
@@ -51,12 +51,12 @@ def get_imap_messages() -> Generator[Message, None, None]:
         mbox.select(settings.EMAIL_GATEWAY_IMAP_FOLDER)
         try:
             status, num_ids_data = mbox.search(None, 'ALL')
-            for msgid in num_ids_data[0].split():
-                status, msg_data = mbox.fetch(msgid, '(RFC822)')
+            for message_id in num_ids_data[0].split():
+                status, msg_data = mbox.fetch(message_id, '(RFC822)')
                 msg_as_bytes = msg_data[0][1]
                 message = email.message_from_bytes(msg_as_bytes)
                 yield message
-                mbox.store(msgid, '+FLAGS', '\\Deleted')
+                mbox.store(message_id, '+FLAGS', '\\Deleted')
             mbox.expunge()
         finally:
             mbox.close()
diff --git a/zerver/tests/test_push_notifications.py b/zerver/tests/test_push_notifications.py
index 20d3338f4f..1b1e2daaad 100644
--- a/zerver/tests/test_push_notifications.py
+++ b/zerver/tests/test_push_notifications.py
@@ -1560,13 +1560,13 @@ class TestClearOnRead(ZulipTestCase):
         hamlet.save()
         stream = self.subscribe(hamlet, "Denmark")
 
-        msgids = [self.send_stream_message(self.example_email("iago"),
-                                           stream.name,
-                                           "yo {}".format(i))
-                  for i in range(n_msgs)]
+        message_ids = [self.send_stream_message(self.example_email("iago"),
+                                                stream.name,
+                                                "yo {}".format(i))
+                       for i in range(n_msgs)]
         UserMessage.objects.filter(
             user_profile_id=hamlet.id,
-            message_id__in=msgids,
+            message_id__in=message_ids,
         ).update(
             flags=F('flags').bitor(
                 UserMessage.flags.active_mobile_push_notification))
@@ -1577,11 +1577,11 @@ class TestClearOnRead(ZulipTestCase):
             queue_items = [c[0][1] for c in mock_publish.call_args_list]
             groups = [item['message_ids'] for item in queue_items]
 
-        self.assertEqual(len(groups), min(len(msgids), max_unbatched))
+        self.assertEqual(len(groups), min(len(message_ids), max_unbatched))
         for g in groups[:-1]:
             self.assertEqual(len(g), 1)
-        self.assertEqual(sum(len(g) for g in groups), len(msgids))
-        self.assertEqual(set(id for g in groups for id in g), set(msgids))
+        self.assertEqual(sum(len(g) for g in groups), len(message_ids))
+        self.assertEqual(set(id for g in groups for id in g), set(message_ids))
 
 class TestReceivesNotificationsFunctions(ZulipTestCase):
     def setUp(self) -> None: