Speaking as someone who knows their way around cryptography and protocols, and has happily hacked on SMTP/POP3/IMAP clients & servers, what *exactly* is the reason why @Tutanota and @protonmail don't support these protocols and/or external clients?
Because all I can see are downsides of this.
Fuck, we shouldn't have to ask for interoperability in 2022.
@gergely in order to send email outside, they have to use understandable aka standards based algorithms.