setting templates breaks mailman
My mailman install stopped working, that is, emails were being accepted but not sent out to list members. They were stuck in the shunt
queue. I spent several hours debugging the mysterious "Cannot connect to SMTP server localhost on port 25". Thankfully, I came across https://lists.mailman3.org/archives/list/mailman-users@mailman3.org/thread/KEAA7RUGNF2BMFHWDJINRAAA4N3OTA2P/ where Manos somehow discovered (by running mailman's 'out' runner in pdb?) that creating templates via the UI somehow broke their emails with the same error message, and I discovered that I too had created templates. Deleting them allowed me to unshunt my messages.
This is on debian 11.6. I am not really sure exactly how things were broken, since getting any kind of debug logging beyond "Cannot connect to SMTP server" seemed ... difficult. I'm opening this issue to help other lost souls like me who may have broken mailman by attempting to create templates, and also maybe someone has a way to fix it? My workaround is to not set templates for now. Let me know if there's something I can do to debug exactly what went wrong, I think it probably has something to do with ports and hosts and the mini-distributed system that is mailman communicating with itself over a "network".