Actually, port 587 is standard—or, at least, a standard. See RFC-4409, "Message Submission for Mail". This goes back 10 years (originally RFC-2476); the idea is to segregate message submission (which should require authentication) from message relay (which should not), and to permit firewalls to tell the difference.
Still, it would be nice if they'd provided some way for MUAs to tell when they should be talking to 587 instead of 25. The RFC doesn't even mention transition issues (!), but I suppose a smart MUA could detect that 25 isn't getting through and offer to try 587.
587 is standard
Actually, port 587 is standard—or, at least, a standard. See RFC-4409, "Message Submission for Mail". This goes back 10 years (originally RFC-2476); the idea is to segregate message submission (which should require authentication) from message relay (which should not), and to permit firewalls to tell the difference.
Still, it would be nice if they'd provided some way for MUAs to tell when they should be talking to 587 instead of 25. The RFC doesn't even mention transition issues (!), but I suppose a smart MUA could detect that 25 isn't getting through and offer to try 587.