I have this idea to buy a .su domain and host my own email addy. I’m sure all the tools to do so exist on Linux but I haven’t taken the time to really research it yet.
If it’s just a newsletter I would set up a mailbox filter that just sends all of their mail to the trash. GMail makes this pretty easy (highlight a spam message, select “filter messages like these” from the top menu), but idk how to do it on other mail servers.
DF is also free and there’s fan made installers to run it on Linux, the Steam version just has an enhanced UI and other features.