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RE: [Asrg] article: port 25 blocking

2005-04-12 07:10:05

On Tue, 12 Apr 2005, Larry Seltzer wrote:

I had a thought yesterday that I wish I had before I hit the publish button
on the article: Perhaps the answer for people who need an exception case for
port 25 blocking is port 587 or even some non-standard port. I checked and
my own mail server supports both. Put SMTP on port 1125 or something like
that for your external users, or use 587 and require authentication. Is
there a reason this wouldn't work?

Several issues:
1. Some locations (specially airport wireless, etc) actually do full
   port filtering in way that only well known ports are open. Anything
   new (and that includes port 587 unfortunetly) is not on their list.
2. A non-standard port that is 100% open just like regular SMTP is bound
   to soon be known and start to be abused. It has to be some type of
   restricted profile smtp with authentication (which is what submit is,
   so why reinvent it...).

---
William Leibzon
  mailto: william(_at_)completewhois(_dot_)com
Anti-Spam and Email Security Research Worksite:
  http://www.elan.net/~william/emailsecurity/
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