port question

[David A. Bandel]

On Sun, Aug 23, 2009 at 15:48, Tony Alfrey<tonyalfrey at earthlink.net> wrote:
> David A. Bandel wrote:
>
>>
>>> 3.  The SMTP *client* in (1) sets a port within the TCP/IP protocol
>>> packets
>>> of the outgoing mail.  If Port 25 is set, it may be rejected by the
>>> outgoing
>>> SMTP *server*, and never re-sent (relayed).  Correct?
>>
>> the smtp client may request a different port, but that would usually
>> be because the network the client is on has port 25 blocked at its
>> border and the smtp server is beyond the border
>
>
> I must select Port 587 for the SMTP server settings when I use my e-mail
> client (SMTP client?), otherwise I cannot get my packets to be accepted by
> my SMTP server (earthlink) or allowed for transmission to my SMTP server by
> my isp (comcast).   But you (and other) sources say that Port 25 is always
> used for internet e-mail.  Does this mean that the port ID in the packets is
> changed from port 587 to port 25 (or additional port 25 headers added) by
> the transmitting SMTP server?
>

Actually, port 587 is the submissions port.  Regardless, you are on
comcast which almost certainly blocks outgoing port 25 from all but
their mail servers, and earthlink is not on their network, so the only
way to directly connect to port 25 on earthlink as a client of comcast
is to hijack a comcast mail server IP -- those are the only ones not
blocked from using port 25 through the border routers.

Don't make this complicated, it's really simple.  If you are comcast,
you deny all your clients port 25 outbound so they if they get a
Windoze spambot virus, they don't spam the world.  They want everyone
to use their mail server as a smarthost and are almost 100% certainly
requiring smtp auth.

I can't make this much clearer.

David A. Bandel
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