Purging smtp services from Debian
Lately I purchased mew dedicated server with intention to use it as my new running mail email server - mailcow, my blog, and some other services. When I was migrating mailcow suite everything was fine except postfix image failed to start.
I had problem like that already on Debian and usually I was dealing with that by disabling exim:
sudo systemctl disable exim.service
This was fine till major Debian update that was reinstalling exim and causing it to steal port 25 again. So this time I decided to uinstall it completely.