You are "that guy". I didn't say we didn't know about this distinction, I said we have a better understanding. It used to be the case submitting originating em

You are "that guy". I didn't say we didn't know about this distinction, I said we have a better understanding. It used to be the case submitting originating email on port 25 was accepted. Now, if you have that configured, it's wildly considered that You're Doing It Wrong™. Many email clients, like Eudora and Thunderbird, were submitting email on port 25 for a long time, in the clear, where the only protection was very loose source IP address restrictions for outbound, otherwise you'd be an open relay. Using different servers for inbound vs outbound mail submission was a relatively rare thing too, because the routing can be a bear to set up. SMTPS (SMTP over SSL) on port 465 wasn't official and was locally used where it could be supported (by the client) and where an admin had bothered to configured it. Many email clients didn't have support for even using a non-standard port for any thing mail related, so even once the mail submission port 587 was standardized it was often a problem getting a client to use it or providing authentication on it. But even the OP is saying that fetchmail is a problem because it's trying to be an a full, transparent MTA when it's really a glorified MUA. The fact that fetchmail (and its ilk) talk MUA protocols to receive email (pop3, imap) and can then turn around and reinject that message into the mail stream using SMTP to implement local delivery is where a lot of the problems with fetchmail come from (such as munging the headers or creating email loops with mailing lists).