I run a OpenSMTPD+Dovecot SMTP server on a rented VPS with my own domain. It /mostly/ runs fine, but when something breaks, that's really annoying. I think using a paid service with your own domain is probably a lot superior from a technical perspective, but I do like to do some weird things with my email that self-hosting allows me to. I definitely wouldn't recommend it if you don't have a decent amount of free time and technical knowledge.