The problem I've been seeing with email on my own domain is that some services refuse it, saying "please enter a real email address" 🤬 some others just silently refuse to send a confirmation code so I can't register either (I think tinder did this). Especially the "not a real email address" really pissed me off.

And with proton I got "Anonimisation services are forbidden" once at least.

I forget which services, but it's Hella annoying..

The marketshare of Google and Microsoft on email is really becoming a problem.