Gettting past spam filters (Linux)

[RedFox1]

We automatically send appointment emails to clients from one of our linux boxes. I have sendmail set up to relay the mail (via "Smart Host") through our MS exchange server.

It works great...but we've noticed that some of our clients don't get the emails, apparently because their corporate firewall sees it as spam.

Any spam gurus out there that could suggest what might be making our email look like spam to them? The "from" is a valid domain...and not one that's been blackholed or anything...

-Russ

 

[notfred]

After reading the email you so generously provided, I can tell you exactly why the spam filter is classifying it how it does.

 

[RedFox1]

Here's a sample header:

X-Apparently-To: russwilliston@yahoo.com via 216.136.226.65; 20 Mar 2003 11:37:05 -0800 (PST)
Return-Path: <rwilliston@aggie3.sbsb.com>
Received: from 12.30.28.8 (EHLO cent08.sbsbmail.com) (12.30.28.8) by mta107.mail.scd.yahoo.com with SMTP; 20 Mar 2003 11:37:05 -0800 (PST)
Received: by CENT08 with Internet Mail Service (5.5.2653.19) id <D8KBVSA1>; Thu, 20 Mar 2003 14:30:46 -0500
Received: from aggie3.sbsb.com (aggie3 [192.168.4.15]) by cent08.sbsbmail.com with SMTP (Microsoft Exchange Internet Mail Service Version 5.5.2653.13) id D8KBVSAD; Thu, 20 Mar 2003 14:30:43 -0500
Received: (from rwilliston@localhost) by aggie3.sbsb.com (8.11.6/8.11.6) id h2KJax429314; Thu, 20 Mar 2003 14:36:59 -0500
From: afakeguy@sbsb.com
To: russwilliston@yahoo.com
Date: Thu, 20 Mar 2003 14:36:59 -0500
Message-Id: <200303201936.h2KJax429314@aggie3.sbsb.com>
Content-Length: 31

 

[RedFox1]

In the above scenario, Aggie3 is a linux box running sendmail. Cent08 is a NT box running exchange.

 

[n0cmonkey]

1. The exchange machine is not an open relay, correct?
2. Have you tried talking to your customers to try and resolve this? Finding out what kinds of spam filters they have in place would be invaluable for correcting this.
3. Have you checked the content of the emails for things that may spring the anti-spam trap?

 

[RedFox1]

Part of our problem is that they clients haven't been too cooperative in trying to work this out... as such I'm forced to take wild stabs and guess at what their filter might be seeing. (They are paying us though...so I'm not complaining too loud.)

The exchange server is configured to relay for the linux server; so no it's not an open relay in that sense. And it relays fine -- other folks recieve the relayed mail without any trouble.

I haven't thought too much about the content actually...It's just a short body and an attached plain-text file. It's worth looking at. (Who knows though; maybe they used some unfortunate word combination like "get rich working from home" ). I'll look into that -- good idea.

Still no luck this morning in any case...been working at this off and on for a while.

-Russ

 

[RedFox1]

Hey I think I worked it out. In the sendmail documentation I found mention of the "Trusted User" file -- I added my linux user to that, rebuilt with m4 and reloaded sendmail. Now the client is recieving my emails.

Apparently Sendmail prevents users not listed in that file from hiding their real return path. Now sendmail is trusting the return-path I give it. Apparently that was the issue.

Thanks for the suggestions, n0cmonkey.

-Russ