I’m on a friend’s mail server with my own domain pointing at it.

That plus a catchall address means I can give out different email addresses to every website, app, and service provider without having to rely on things like Gmail’s plus addresses being accepted. That makes it really easy to tell who leaked my address to spammers – and to filter out the resulting spam.

Add to that Thunderbird’s built-in address spoofing functionality and I can even do that for outgoing mail.

So whether you go self-hosted or have a provider that allows custom domains, I can really recommend setting one up. They’re not too expensive (unless you go with some of the more exotic gTLDs) and I consider hassle-free per-service email addresses to be a game changer.