Process monthly membership reminder bounces against member lists.

Mailman/Defaults.py.in

@@ -836,12 +836,16 @@ VERP_PROBES = No
 
 # A perfect opportunity for doing VERP is the password reminders, which are
 # already addressed individually to each recipient.  Set this to Yes to enable
-# VERPs on all password reminders.  However, because password reminders are
-# sent from the site list and site list bounces aren't processed but are just
-# forwarded to the site list admins, this isn't too useful.  See comments at
-# lines 70-84 of Mailman/Queue/BounceRunner.py for why we don't process them.
+# VERPs on all password reminders.  This is useful when
+# BOUNCE_PROCESS_REMINDER_BOUNCES is enabled.
 VERP_PASSWORD_REMINDERS = No
 
+# When a monthly membership/password reminder bounces, register the bounce
+# against every list the member is subscribed to that sends reminders and has
+# bounce processing enabled.  Other site list bounces (e.g. owner moderation
+# notices) are still forwarded to the site list administrators.
+BOUNCE_PROCESS_REMINDER_BOUNCES = Yes
+
 # Another good opportunity is when regular delivery is personalized.  Here
 # again, we're already incurring the performance hit for addressing each
 # individual recipient.  Set this to Yes to enable VERPs on all personalized

Mailman/Queue/BounceRunner.py

@@ -23,12 +23,14 @@
 import time
 import pickle
 
+from email.iterators import typed_subpart_iterator
 from email.mime.text import MIMEText
 from email.mime.message import MIMEMessage
 from email.utils import parseaddr
 
 from Mailman import mm_cfg
 from Mailman import Utils
+from Mailman.MailList import MailList
 from Mailman import LockFile
 from Mailman.Errors import NotAMemberError
 from Mailman.Message import UserNotification
@@ -74,8 +76,9 @@ def __init__(self):
         # site list's bounce address.  The bounce runner would then dutifully
         # register a bounce for all 4 lists that aperson@example.com was a
         # member of, and eventually that person would get disabled on all
-        # their lists.  So now we ignore site list bounces.  Ce La Vie for
-        # password reminder bounces.
+        # their lists.  So now we ignore most site list bounces.  Membership
+        # reminder bounces can optionally be processed; see
+        # BOUNCE_PROCESS_REMINDER_BOUNCES.
         self._bounce_events_file = os.path.join(
             mm_cfg.DATA_DIR, 'bounce-events-%05d.pck' % os.getpid())
         self._bounce_events_fp = None
@@ -97,6 +100,22 @@ def _queue_bounces(self, listname, addrs, msg):
         os.fsync(self._bounce_events_fp.fileno())
         self._bouncecnt += len(addrs)
 
+    def _queue_reminder_bounces(self, addr, msg):
+        """Queue a reminder bounce for each subscribed list that sends reminders."""
+        for listname in Utils.list_names():
+            if listname.lower() == mm_cfg.MAILMAN_SITE_LIST.lower():
+                continue
+            mlist = MailList(listname, lock=0)
+            if not mlist.bounce_processing:
+                continue
+            if not mlist.send_reminders:
+                continue
+            if not mlist.isMember(addr):
+                continue
+            if mlist.getMemberOption(addr, mm_cfg.SuppressPasswordReminder):
+                continue
+            self._queue_bounces(listname, [addr], msg)
+
     def _register_bounces(self):
         syslog('bounce', '%s processing %s queued bounces',
                self, self._bouncecnt)
@@ -206,18 +225,24 @@ def _dispose(self, mlist, msg, msgdata):
         # message sent directly to the -bounces address.  We have to do these
         # cases separately, because sending to site-owner will reset the
         # envelope sender.
+        is_site_list = (mlist.internal_name().lower() ==
+                        mm_cfg.MAILMAN_SITE_LIST.lower())
+        process_reminder_bounce = False
         # Is this a site list bounce?
-        if (mlist.internal_name().lower() ==
-                mm_cfg.MAILMAN_SITE_LIST.lower()):
-            # Send it on to the site owners, but craft the envelope sender to
-            # be the -loop detection address, so if /they/ bounce, we won't
-            # get stuck in a bounce loop.
-            outq.enqueue(msg, msgdata,
-                         recips=mlist.owner,
-                         envsender=Utils.get_site_email(extra='loop'),
-                         nodecorate=1,
-                         )
-            return
+        if is_site_list:
+            if (mm_cfg.BOUNCE_PROCESS_REMINDER_BOUNCES and
+                    is_membership_reminder_bounce(msg)):
+                process_reminder_bounce = True
+            else:
+                # Send it on to the site owners, but craft the envelope sender
+                # to be the -loop detection address, so if /they/ bounce, we
+                # won't get stuck in a bounce loop.
+                outq.enqueue(msg, msgdata,
+                             recips=mlist.owner,
+                             envsender=Utils.get_site_email(extra='loop'),
+                             nodecorate=1,
+                             )
+                return
         # Is this a possible looping message sent directly to a list-bounces
         # address other than the site list?
         # Check From: because unix_from might be VERP'd.
@@ -233,7 +258,7 @@ def _dispose(self, mlist, msg, msgdata):
                          )
             return
         # List isn't doing bounce processing?
-        if not mlist.bounce_processing:
+        if not process_reminder_bounce and not mlist.bounce_processing:
             return
         # Try VERP detection first, since it's quick and easy
         addrs = verp_bounce(mlist, msg)
@@ -268,7 +293,11 @@ def _dispose(self, mlist, msg, msgdata):
         # can let None's sneak through.  In any event, this will kill them.
         # addrs = filter(None, addrs)
         # MAS above filter moved up so we don't try to queue an empty list.
-        self._queue_bounces(mlist.internal_name(), addrs, msg)
+        if process_reminder_bounce:
+            for addr in addrs:
+                self._queue_reminder_bounces(addr, msg)
+        else:
+            self._queue_bounces(mlist.internal_name(), addrs, msg)
 
     _doperiodic = BounceMixin._doperiodic
 
@@ -277,6 +306,40 @@ def _cleanup(self):
         Runner._cleanup(self)
 
 
+
+def is_membership_reminder_bounce(msg):
+    """Return true if this bounce is for a monthly membership reminder."""
+    for part in typed_subpart_iterator(msg, 'message', 'rfc822'):
+        orig = part.get_payload(0)
+        if orig is None:
+            continue
+        if orig.get('X-Mailman-Membership-Reminder', '').lower() == 'yes':
+            return True
+        if orig.get('x-list-administrivia', '').lower() != 'yes':
+            continue
+        sender = parseaddr(orig.get('from', ''))[1].lower()
+        if not sender:
+            continue
+        # Owner notifications are sent from the site -bounces address.
+        if _is_site_bounces_address(sender):
+            continue
+        subj = Utils.oneline(orig.get('subject', ''), 'us-ascii').lower()
+        if 'reminder' in subj:
+            return True
+    return False
+
+
+
+def _is_site_bounces_address(addr):
+    addr = addr.lower()
+    mailbox, domain = Utils.ParseEmail(addr)
+    if mailbox == '%s-bounces' % mm_cfg.MAILMAN_SITE_LIST:
+        return True
+    if mailbox.startswith('%s-bounces+' % mm_cfg.MAILMAN_SITE_LIST):
+        return True
+    return False
+
+
 
 def verp_bounce(mlist, msg):
     bmailbox, bdomain = Utils.ParseEmail(mlist.GetBouncesEmail())

cron/mailpasswds

@@ -225,6 +225,7 @@ def main():
             finally:
                 i18n.set_translation(otrans)
             msg['X-No-Archive'] = 'yes'
+            msg['X-Mailman-Membership-Reminder'] = 'yes'
             del msg['auto-submitted']
             msg['Auto-Submitted'] = 'auto-generated'
             # We want to make this look like it's coming from the siteowner's

tests/test_bounce_reminders.py

@@ -0,0 +1,139 @@
+# Copyright (C) 2026 by the Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+
+"""Test membership reminder bounce handling."""
+
+import os
+import pickle
+import unittest
+import email
+
+_TESTDIR = os.path.dirname(os.path.abspath(__file__))
+try:
+    from Mailman import __init__
+except ImportError:
+    import paths
+
+from Mailman import Utils
+from Mailman.Queue.BounceRunner import is_membership_reminder_bounce
+
+
+SAMPLE = os.path.join(
+    _TESTDIR, 'bounces', 'samples_from_messages',
+    'sample_01_undelivered_mail_returned_to_sender.eml')
+
+
+
+class ReminderBounceTest(unittest.TestCase):
+    def test_membership_reminder_sample(self):
+        if not os.path.exists(SAMPLE):
+            self.skipTest('sample bounce file not available')
+        with open(SAMPLE, 'rb') as fp:
+            msg = email.message_from_binary_file(fp)
+        self.assertTrue(is_membership_reminder_bounce(msg))
+
+    def test_owner_notification_is_not_reminder(self):
+        msg = email.message_from_string("""\
+Content-Type: multipart/report; boundary="BOUND"
+
+--BOUND
+Content-Type: text/plain
+
+A moderation notice bounced.
+
+--BOUND
+Content-Type: message/rfc822
+
+From: mailman-bounces@dom.ain
+To: mylist-owner@dom.ain
+Subject: Your message awaits moderator approval
+X-List-Administrivia: yes
+
+The held message.
+
+--BOUND--
+""")
+        self.assertFalse(is_membership_reminder_bounce(msg))
+
+    def test_explicit_header(self):
+        msg = email.message_from_string("""\
+Content-Type: multipart/report; boundary="BOUND"
+
+--BOUND
+Content-Type: message/rfc822
+
+From: mailman-owner@dom.ain
+To: user@example.com
+Subject: anything
+X-Mailman-Membership-Reminder: yes
+
+Reminder body.
+
+--BOUND--
+""")
+        self.assertTrue(is_membership_reminder_bounce(msg))
+
+
+
+class ReminderBounceQueueTest(unittest.TestCase):
+    def test_queue_reminder_bounces(self):
+        from Mailman.Queue.BounceRunner import BounceMixin
+        import Mailman.Queue.BounceRunner as br_mod
+        from Mailman import mm_cfg
+
+        class FakeList(object):
+            bounce_processing = 1
+            send_reminders = 1
+
+            def isMember(self, addr):
+                return addr == 'user@example.com'
+
+            def getMemberOption(self, addr, option):
+                return 0
+
+        class TestMixin(BounceMixin):
+            pass
+
+        runner = TestMixin()
+        msg = email.message_from_string('Subject: bounce\n\n')
+        old_list_names = Utils.list_names
+        old_mail_list = br_mod.MailList
+        try:
+            Utils.list_names = lambda: [mm_cfg.MAILMAN_SITE_LIST, 'mylist']
+            br_mod.MailList = lambda name, lock=0: FakeList()
+            runner._queue_reminder_bounces('user@example.com', msg)
+        finally:
+            Utils.list_names = old_list_names
+            br_mod.MailList = old_mail_list
+
+        runner._bounce_events_fp.seek(0)
+        events = []
+        while True:
+            try:
+                events.append(pickle.load(runner._bounce_events_fp))
+            except EOFError:
+                break
+        self.assertEqual(len(events), 1)
+        self.assertEqual(events[0][0], 'mylist')
+        self.assertEqual(events[0][1], 'user@example.com')
+        runner._bounce_events_fp.close()
+        os.unlink(runner._bounce_events_file)
+        runner._bounce_events_fp = None
+        runner._bouncecnt = 0
+
+
+
+def suite():
+    suite = unittest.TestSuite()
+    suite.addTest(unittest.makeSuite(ReminderBounceTest))
+    suite.addTest(unittest.makeSuite(ReminderBounceQueueTest))
+    return suite
+
+
+
+if __name__ == '__main__':
+    unittest.main(defaultTest='suite')