FYI: in the mailman log was also the following traceback
Mar 04 14:08:24 2021 (5044) Traceback (most recent call last): File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/core/runner.py", line 173, in _one_iteration self._process_one_file(msg, msgdata) File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/core/runner.py", line 266, in _process_one_file keepqueued = self._dispose(mlist, msg, msgdata) File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/runners/pipeline.py", line 37, in _dispose process(mlist, msg, msgdata, pipeline) File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/core/pipelines.py", line 50, in process handler.process(mlist, msg, msgdata) File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/handlers/member_recipients.py", line 84, in process for member in mlist.regular_members.members File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/handlers/member_recipients.py", line 83, in <genexpr> recipients = set(member.address.email File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/model/roster.py", line 239, in members yield from self._get_members(DeliveryMode.regular) File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/model/roster.py", line 226, in _get_members if member.delivery_mode in delivery_modes: File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/model/member.py", line 212, in delivery_mode return self._lookup('delivery_mode') File "/opt/mailman/mm/venv/lib/python3.7/site-packages/mailman/model/member.py", line 174, in _lookup pref = getattr(self.address.preferences, preference) AttributeError: 'NoneType' object has no attribute 'preferences' Mar 04 14:08:24 2021 (5044) SHUNTING: 1614866904.2741017+f1f320a5d0006e885586be5b33543e364e3829b4