Hl mailman-users!

The LMTP runner on my Mailman 3 install (3.1.0b4) has started silently crashing. The parent process and all of the other runners stay up. Nothing interesting seems to be written to the logs. I've been finding out about it when exim4 (running on the same server) starts sending out "retry timeout exceeded" bounce emails to list participants:

From: Mail Delivery System [mailto:Mailer-Daemon@lists.mysite.org]

Sent: Monday, July 31, 2017 12:39 PM To: some_participant@mysite.org Subject: Mail delivery failed: returning message to sender

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

listname@lists.mysite.org retry timeout exceeded

Action: failed Final-Recipient: rfc822;listname@lists.mysite.org Status: 5.0.0

After hearing about the bounces from participants, I then SSH to the lists server and attempt to telnet localhost 8024 but get no response. The LMTP runner is not listed in ps -ef. After restarting all of mailman (mailman stop; mailman start) I get the 220 response from LMTP on port 8024. I see the LMTP runner in ps -ef.

Does anyone have any ideas on how I could start debugging this?

Thank you,

Mark