Is your ISP blocking outgoing port 25?

Steven King sking at
Fri Jun 19 22:35:00 UTC 2009

Most MTAs don't come preconfigured with port 587 either. It is amazing
how many people/organizations go with the "if it isn't broke, don't fix
it" mentality, even though it clearly needs to be revised and something
new needs to be done/supported. Email needs to be revamped on a larger
scale than just adding standards.

Sean Donelan wrote:
> On Fri, 19 Jun 2009, Jeroen Wunnink wrote:
>> 1. Customers remember it more easily
>> 2. Some ISP's also block 587 (hence 'SMTP ports' rather then 'SMTP
>> port' in my previous comment ;-)
> Those same clueless ISPs will probably block 2525 someday too,
> clueless expands to fill any void.  And using non-standard things like
> 2525 only lead to more confusion for customers later when they try
> someone else's non-standard choice, e.g. port 26 or 24 or 5252 and
> wonder why those don't work.
> On the other hand, why don't modern mail user agents and mail transfer
> agents come configured to use MSA port 587 by default for message
> submission instead of making customers remember anything? RFC 2476 was
> published over a decade ago, software developers should have caught up
> to it by now.  Imagine if the little box in Outlook and Exchange had
> the MSA port already filled in, and you only needed to change it for
> legacy things.

Steve King

Network Engineer - Liquid Web, Inc.
Cisco Certified Network Associate
CompTIA Linux+ Certified Professional
CompTIA A+ Certified Professional

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