Why do so few mail providers support Port 587?

Wed Feb 16 14:20:44 UTC 2005

At 04:42 AM 2/16/2005, Owen DeLong <owen at delong.com> wrote:
>If you accept unauthenticated mail on port 587, the problem isn't the
>spam you will receive, it is the spam you will forward.

ONLY if that unauthenticated sender is also permitted to RELAY.

That is not a given. The decision to relay or not is separate from whether 
the user is authenticated with SMTP AUTH or some other method (IP address 
range, smtp-after-pop), just as it is on port 25.

I'm not arguing for leaving port 587 wide open, but there are uses to 
allowing potr 587 and 25 to have the same rules, and not permit relay on 
either. This is necessary where SMTP-after-POP is still in use, for 
example, but does NOT imply open relay. Yes, authorized users (authorized 
by AUTH, smtp-after-pop, or IP address ranges) can still send mail 
(including spam, subject to enforcement) but that does NOT constitute open 
relay. 