Hello, I have a postfix v3.5.17 MTA running alongside the Request Tracker application inside of a Docker container. It receives mail bound for RT forwarded from Google Workspace’s MX.
This deployment has worked for two years, but on or around December 16th, no longer responds to new SMTP connections. There was no update to the container, and neither to the docker host environment (as far as I can tell), and the container has since been deleted and recreated (and container image deleted and re-pulled) without any improvement. I believe I have eliminated network/firewall as the source of the issue, as I can reproduce it easily by issuing `telnet localhost 25` from within the container — the TCP connection is established, but postfix never sends its SMTP 220. My analysis thus far is that the following occurs: 1. Postfix starts and the `master` process binds to port 25 2. A TCP connection is opened to port 25; master responds by spawning an smtpd 3. smtpd -v logs that it starts up but never shows any evidence of being aware that it has a connection to accept and takes no action. 4. netstat/ss -tula shows that the Recv-Q value for the listening TCP port 25 increments whenever a connection attempt is made. In a tcpdump, the TCP three-way-handshake occurs, but no further communication occurs until the client times out and closes the stream. I would not say I am completely stumped yet as I have a number of things I want to try including tracing syscalls as recommended by the postfix troubleshooting documentation (this is made slightly complicated by running in a container). I have also not yet fully determined the parameters of where the issue appears — I can not yet reproduce it in a container running outside of the production environment, and I still need to try spinning up a similar container in the same host environment to see if it has the same issue or if I can diff my way to an isolated cause. That said I’m not super experienced with postfix so any help that might be able to point me in the right direction would be appreciated. As I collect more information and complete more of the troubleshooting steps I will supplement this post with additional debug information. Thank you, -- Nicholas Reilingh, Database and Systems Manager Fisher Center at Bard | fishercenter.bard.edu _______________________________________________ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
