A way to migrate to a smaller “instance” is by using a synology nas with enough bays. You could split them by using ssd hdd raids and dockerize all applications or even create vm on it

could you paste your docker-compose file ? This would help a bit.

yea absuing it as a shopping list for private stuff and the kanban as tasks for work 😅

Running a mail server these days is not that difficult. While using pre-assembled stacks like mailcow only the DNS entries needs to be done. If you want to run it at home you should do some research on routing all the traffic through a wireguard tunnel to preserve a public IP other mail instances will accept