/usr/lib/python3/dist-packages/mailman/mta/ is in mailman3 3.1.1-9.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python3/dist-packages/mailman/mta/__init__.py
/usr/lib/python3/dist-packages/mailman/mta/aliases.py
/usr/lib/python3/dist-packages/mailman/mta/base.py
/usr/lib/python3/dist-packages/mailman/mta/bulk.py
/usr/lib/python3/dist-packages/mailman/mta/connection.py
/usr/lib/python3/dist-packages/mailman/mta/decorating.py
/usr/lib/python3/dist-packages/mailman/mta/deliver.py
/usr/lib/python3/dist-packages/mailman/mta/docs/
/usr/lib/python3/dist-packages/mailman/mta/docs/__init__.py
/usr/lib/python3/dist-packages/mailman/mta/docs/authentication.rst
/usr/lib/python3/dist-packages/mailman/mta/docs/bulk.rst
/usr/lib/python3/dist-packages/mailman/mta/docs/connection.rst
/usr/lib/python3/dist-packages/mailman/mta/docs/decorating.rst
/usr/lib/python3/dist-packages/mailman/mta/docs/mta.rst
/usr/lib/python3/dist-packages/mailman/mta/docs/personalized.rst
/usr/lib/python3/dist-packages/mailman/mta/docs/verp.rst
/usr/lib/python3/dist-packages/mailman/mta/exim4.py
/usr/lib/python3/dist-packages/mailman/mta/null.py
/usr/lib/python3/dist-packages/mailman/mta/personalized.py
/usr/lib/python3/dist-packages/mailman/mta/postfix.py
/usr/lib/python3/dist-packages/mailman/mta/tests/
/usr/lib/python3/dist-packages/mailman/mta/tests/__init__.py
/usr/lib/python3/dist-packages/mailman/mta/tests/test_aliases.py
/usr/lib/python3/dist-packages/mailman/mta/tests/test_connection.py
/usr/lib/python3/dist-packages/mailman/mta/tests/test_delivery.py
/usr/lib/python3/dist-packages/mailman/mta/verp.py