[NCLUG] comcast blocking port 25?

DJ Eshelman djsbignews at gmail.com
Thu Mar 22 00:48:46 MDT 2007


Okay... so I've been away from the list for awhile...

I had a thought about all this, something I ran into recently.

Most mail servers these days (mine included) are doing reverse DNS lookups,
which means if you are sending from your own machine on Comcast's network
you would not have a valid reverse DNS, and the mail server would either
reject your email or send the SA score thru the roof.  In fact, we host
email for several small businesses and serve as their mail relay for POP for
this reason.  It's always best to relay thru your ISPs mailserver, as long
as it doesn't do anything funky like change your reply-to information
(something that gmail does, as I found out recently).

food for thought :)

-DJ

On 3/8/07, Sean Reifschneider <jafo at tummy.com> wrote:
>
> On Wed, Mar 07, 2007 at 09:19:52AM -0700, Matt wrote:
> >be blocked? My understanding is that port 587 should be used. Should I
> >configure postfix to look at both 25 and 587?  If so, how?
>
> 587 should be used, if comcast suggests it, for outgoing mail.  That is
> "mail submission" which is different than incoming SMTP (port 25).
> This is supposed to be so that a mail server can deal with it's own users,
> sending outgoing mail, differently than it deals with incoming e-mail.
>
> Sean
> --
> We are all in the gutter, but some of us are looking at the stars.
>                  -- Oscar Wilde
> Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
> tummy.com, ltd. - Linux Consulting since 1995: Ask me about High
> Availability
>
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