North American Network Operators Group

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Why do so few mail providers support Port 587?

  • From: Sean Donelan
  • Date: Tue Feb 15 21:03:41 2005

Although RFC2476 was published in December 1998, its amazing
how few mail providers support the Message Submission protocol
for e-mail on Port 587.  Even odder, some mail providers
use other ports such as 26 or 2525, but not the RFC recommended
Port 587 for remote authenticated mail access for users.

Large mail providers like AOL, GMAIL and Yahoo support authenticated
mail on port 587; and some also support Port 465 for legacy SMTP/SSL.
But a lot of universities and smaller mail providers don't.  They
still use SMTP Port 25 for roaming users.  With AT&T, Earthlink, COX,
Netzero and other ISPs filtering port 25 for years, I would have thought
most mail providers would have started supporting Port 587 by now.

What can be done to encourage universities and other mail providers
with large roaming user populations to support RFC2476/Port 587?
What can be done to encourage the mail client software programers (i.e.
Outlook, Eudora, etc) to make Port 587 the default (or at least the
first try) and let the user change it back to port 25 (or automatically
fallback) if they are still using a legacy mail server.

Sendmail now includes Port 587, although some people disagree how
its done.  But Exchange and other mail servers are still difficult
for system administrators to configure Port 587 (if it doesn't say
click here for Port 587 during the Windows installer, its too