Mark, please correct if I'm wrong but is the log data below produced by LMTP via Mailman core? This is from the Mailman smtp.log file. Could this somehow be an issue with how we've configured Mailman for LMTP?
Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) >> b'LHLO aeedf7ad9f48.caltech.edu' Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) >> b'MAIL FROM:<snap_wl-bounces+mailman=caltech.edu@caltech.edu> SIZE=4289' Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) sender: snap_wl-bounces+mailman=caltech.edu@caltech.edu Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) >> b'RCPT TO:<mailman@lists.caltech.edu>' Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) recip: mailman@lists.caltech.edu Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) >> b'DATA' Feb 01 21:36:45 2022 (289) ('127.0.0.1', 36132) >> b'QUIT'