Fred Stluka on 23 Jan 2009 14:04:23 -0800

[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]

Re: [PLUG] Comcast and port 25

Short answers:
- Try port 587.  It may already work at the SMTP server.
- Try port 587 at Comcast's SMTP server.
- Leave the laptops configured like this all the time.  May not
  need to switch back and forth at home vs. work.

Long answer:

Yeah, Comcast is doing this to lots of customers lately, supposedly
due to spam, but not really justified on a case by case basis as far
as I can tell.  Seems to happen to people who use their Comcast IP
connection to access any SMTP server other than Comcast via port 25.

This is a really simplistic approach to reducing spam.  Comcast
assumes (perhaps rightly in most cases -- based on the number of
spam bots out there -- but not rightly in my case and the others I
know), that if your computer uses a Comcast IP address to access
a non-Comcast SMTP server on port 25, it must be happening without
your knowledge by a virus that hits lots of unprotected SMTP servers
to flood the world with spam.  They don't seem to take into account
the volume of traffic, the number of non-Comcast SMTP servers you
hit, or anything else.

They block port 25, and send you an e-mail suggesting you download
and run a tool to fix the problem.  I'm not sure what the tool does
other than switch you to port 587, but I don't like running black
box "fixes" like that on my computers.  Instead, I went to my
corporate SMTP server (which uses an official Verizon business-class
SDSL line, not my home Comcast connection), and configured it to
listen on a different port.  Problem solved.

Then I called Comcast and complained, since I shouldn't have had to
do that and because I do occasionally need to be able to hit port
25 at other servers where I have e-mail accounts (Comcast, Voicenet,
Network Solutions, etc.).  Also, I support other users who have
Comcast at home and have to use it to hit port 25 at my corporate
SMTP server and others.  The Comcast support guy told me to move to
port 587.  I said that wouldn't work because I needed to access SMTP
servers that weren't listening on port 587.  He then agreed to
re-open port 25, but said that they had automated processes that
would likely close it again.  Two days later it was closed again. 
I called back and had it re-opened.  Closed again soon.  Grrr!!!

I gave up and tried switching to port 587 at some of my other
target SMTP servers.  Seems to work pretty much everywhere.
I have an 8-year old /etc/services file on an old Linux box that
identifies port 587 as the "mail message submission" port, so I
guess 587 has been used for that for a long time. 

Soon, the spammers and virus writers will move from 25 to 587, and
we'll need a better solution.  However, for now, this simplistic
change is a workaround to the problems caused by Comcast's simplistic

Hopefully, Comcast is better about their business-class accounts.
Fred Stluka -- --
Bristle Software, Inc -- -- Glad to be of service!

Glenn Kelley wrote:
our hosting organization runs on a few ports simply due to how the  
ISP's have started blocking.

We used to run 25/26 but of course some have gotten wise to that - so  
now its 25/26/ and a few others
This begs me to wonder what comcast will do when they release that  
fast speed stuff for business accounts later this quarter.

50/down 20up with 5 static ip's i think is supposed to be the offer.
$200 or so a month

will they block ports on there?
be really cruddy if they do.

Current business accounts however do allow port 25

On Jan 23, 2009, at 1:25 PM, Matt Mossholder wrote:

----- "jeff" <> wrote:
Yeah, as I got more info, I realized what was going on.
Comcast asked me to use the alt port for their smtp server.
Work won't be interested in changing their port though.

No need to "change"... run on both!

Philadelphia Linux Users Group         --
Announcements -
General Discussion  --

Philadelphia Linux Users Group         --
Announcements -
General Discussion  --

Philadelphia Linux Users Group         --
Announcements -
General Discussion  --