comcast, port 25, and postfix?

[Johan Swensson]

Port 25 is also used for receiving mail.
My guess is your ISP blocked port 25 for incoming connections due to someone using your postfix for relaying spam. 


----- Original Message -----
From: "Tom Horsley" <tom.horsley at att.net>
To: "Fedora List" <fedora-list at redhat.com>
Sent: Thursday, May 14, 2009 2:37:51 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: comcast, port 25, and postfix?

I'm running postfix rather than sendmail, and I have it
setup to use a relayhost to send mail via my ISP through
a stunnel SSL connection.

I just got mail from comcast telling me they have blocked
port 25 on my cablemodem due to possible abuse (I don't
really care if they do this - I'm not using port 25).

Just curious: Anyone know if postfix will try to talk port
25 for any reason if I've got it configured to send
via the relay? Or is this just comcast trying to sound
like they have a good reason to do what they always
wanted to do and block smtp :-)? Or are there maybe
obscure kerneloops or smolt or bugbuddy things trying
to talk port 25 directly sometimes?

I've never noticed any port 25 activity in wireshark when
monitoring interfaces while sending mail.