Webone blocking port 25??

Matthew Hawkins matt at mh.dropbear.id.au
Fri Jul 26 11:44:08 EST 2002

This is a resend with certain phrases munged so as to avoid tripping
lists.samba.org's anal spam filter.


----- Forwarded message from Matthew Hawkins <matt at mh.dropbear.id.au> -----

From: Matthew Hawkins <matt at mh.dropbear.id.au>
To: linux at lists.samba.org
Subject: Re: Webone blocking port 25??

Kim Holburn (kim.holburn at anu.edu.au) wrote:
> Your ISP's SMTP server usually won't relay mail unless the "From: " address is a local account.

If this is true for your ISP, seriously consider changing.  Taking the
value of the MUA-specified From: header to perform any kind of relay
testing is stupid to say the least.

It is NOT the job of an MUA to relay mail.  Relaying mail is the job of
an MTA, and there's already perfectly good information obtained from an
SMTP client connection and the message envelope to make a routing

As one good reason not to accept relaying for local addresses specified
in the From: header, you become an open relay.  Just spoof a "local"
address in there when connecting to such a grossly misconfigured SMTP
server, and it'll happily bounce your important p*n*s-*nl*rg*ng, general
from Nig*ri* message to all 50,000 recipients.

The From: header is *meant* to be spoofed.  That's it's sole purpose.
Anyone thinking that it should in any way be remotely connected to the
current active IP connection on the host at the time is smoking crack,
and should seriously consider becoming a lawyer or politician or
similarly close-minded, limited view "professional".

"So, logically, if she weighs the same as a duck, she's made of wood, and therefore a witch!"
(Monty Python and the Holy Grail)

----- End forwarded message -----

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