I've been selfhosting for like dunno 10-15 years. Cheap kimsufi box, opensmtp, dovecot, later then rspamd, done. Never really had a problem. At one point telekom.de blocked my mailserver. I contacted them via postmaster@telekom.de (or something) explaining that while kimsufix boxes are notorious for shady stuff, this is actually a legit mailserver and they whitelisted me shortly after (yeah I was surprised too how smooth that went). So, yeah, can't confirm all the troubles everyone seems to get on about. However I do own the kimsufi box (and the corresponding IP) for a long time now, so maybe I'm just lucky.