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From: Doug Hardie <bc979@lafn.org>
Date: Sun, 6 Jun 2004 09:28:35 -0700
To: Mark <admin@asarian-host.net>
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cc: Gerard Seibert <gerard-seibert@rcn.com>
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Subject: Re: Changing SendMail Port Number
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On Jun 5, 2004, at 17:35, Mark wrote:

> Gerard Seibert wrote:
>
>> This is probably a stupid question, but how do I change the SMTP port
>> number that SendMail listens in on? I want to change it to something
>> else, like perhaps 24. My ISP is blocking 25 and I want to get around
>> that problem.
>
> And how will clients (the world) find you then, on port 24?
>
> Besides, are you sure your ISP blocks *incoming* port 25? That is 
> somewhat
> unusual; *outgoing* 25, yes (for dialup users), but incoming? 
> Regardless,
> same difference: you can start sending on port 24, but since the world 
> is
> listening on port 25, that will do you little good.

There are ISPs out there that block port 25 to any destination other 
than their mail server.  If you are connected to one of them there is 
no way to access your ISP's mail server.  Thats why we provide support 
for both ports 25 and 26.  I have never seen port 26 blocked.  Almost 
all mail clients provide the ability to change the port it uses.  We 
provide instructions to our users on how to make that change if they 
need it sl that they can send mail through our server.  We do require 
the use of SMTP-AUTH to avoid an open relay.  Blocking port 25 is an 
attempt to prevent the use of open relays.