so let me get this straight: @protonmail fucks with customers' eMails?
That's a huge no-go IMHO because that's just inexcuseable!

Not that I'd consider #ProtonMail at all but it's just a big red flag to me even if I were to use them, because if a provider is #paywalling #IMAP & #SMTP they should be better than any generic "#Freemailer" that doesn't.
Because that makes it useless for a lot of my tech stack: What's the point of an eMail provider if I can't use it with a #Zulip server?