I admit it’s sometimes painful to self-host your SMTP service, but that’s because it was very painless to send massive amounts of spam and very painful to throttle and filter messages, but we have much better tooling now.
Self-hosted receiving is also very reliable. Only when you send from your server you might have blacklisting problems. But so many applications today are receive-only - every website signup.
It's only really "very reliable" if you use Google or Microsoft for email, since they are the arbitrator of modern email.