Hi Abhilash,
excuse my delay, i was out-of-order in the last weeks.
You want the URL at which Postorius (postorius) is available from Core (mailman-core container). The default for that in the container images is set to http://mailman-web:8000. Does that not work for you? I changed the container-names (but not the hostnames) an probably i set the POSTORIUS_TEMPLATE_BASE_URL to the container-name and not to the hostname.
If you want to verify, you want to exec into the Core’s container (docker exec -it mailman-core bash) and see if you can curl the URL from inside there. If you are using the default docker-compose-postorius.yaml then there is a /etc/hosts entry created by docker for the mailman-web container, hence http://mailman-web:8000 works there (but it won’t work on the host, since docker doesn’t modify the host’s /etc/hosts). I modified the compose-file since i have a separate container for a database and i use a seperate network for all my other container. The consequence was, that i do not have a fix subnet. I tried to change all occurences of ip-adresses to hostnames. Therefore i stripped these parts in the compose-file. Currently, there is not entry for mailman-web in the hosts file of mailman-core. I did not find any place in your config and scripts, were this file is written. At which place, this should be done? An interesting point: mailman_core has an entry to itself (with own ip) in /etc/hosts and mailman_web also. I think, this is not correct, isnt it? But nevertheless a curl of the URL from core to web works without error message.
There might also be a bug in play here which would cause such connection refused errors when subscribing/unsubscribing when there was a template configured for the list. Is that the case for you or are you seeing always when trying to send the email (which would imply that the Web container simply isn’t reachable from Core). I thought about the situation, that all my lists where migrated from mailman 2. Many of the have footer- and header-messages, automatic replies which are not shown in the template section of the list. Is a recreation in mailman3 a good option in this situation?
Best regards, chrclaus