I solved it with mailcow dockerized and an LT2P service for a non residential static IP. Works great, regular updates & patches and super reliable.

You can set up a fallback using their supplied script to make a cold backup in the cloud if you need to, but I’ve never had to bother. I also use another of their scripts to properly dump the db and files to my NAS and then I use borg to copy all the things to Hetzner.

Not difficult with amazing software like mailcow