June 19, 2025
10:42 p.m.
It takes time to figure out a new feature. I see what is happening. :-) Or, merely one step further.
After a template is stored in the DB you can remove POSTORIUS_TEMPLATE_BASE_URL because the value is cached in the DB. That explains the caching.
Next, without POSTORIUS_TEMPLATE_BASE_URL, it assumes http://localhost:8000/mailman3/ . On our server this is not correct, because it's listening on a unix socket, as well as 80 and 443, but not 8000.