This may or may not be controversial, but I propose that a
requirement for sane operations is that mail-ng be single hop.
Multi-hop was a good design 20 years ago when many entities were not
online all the time, but it has also proven to be a huge hurdle in
it also hurts reliability and makes it difficult to get some kinds of
service that we'd like to have - such as the ability to get immediate
confirmation of delivery and the ability to negotiate content between
sender and receiver (without having to trust an intermediary to do
though I doubt that single hop is quite achievable. I do think that
sndr MUA -> submission MTA -> rcpt MTA/message-store -> rcpt MUA
is fairly reasonable.
I don't see that this is a requirement, but I do think it would be
a useful design choice if we could make it work.
He not busy being born, is busy dying. - Bob Dylan