Which reminds me. How is a MUA supposed to find its submit server?
The same way an MUA finds an SMTP server to submit mail.
Can one, for example, do some SRV DNS lookup?
What would form the lookup key? It doesn't have anything inherent to do
with the user's From address (which after all can vary from one message
to another), nor does it have anything inherent to do with the user's
ISP (I use 4 different ISPs at different times, but I want to keep the
same email address and submission server no matter what ISP I'm using).
He not busy being born, is busy dying. - Bob Dylan