The basis of all mail troubleshooting is a little thing called the Full Mail Header:
http://support.kavi.com/khelp/dotorg/user_help/html/kavi_glossary.html#gloss_full_header
Coordinated with your server logs, and grep you will optimally find out what is happening.
Hopefully, you are also running a nice acceptable AVG and spamassassin/clamav?
http://free.avg.com/download?prd=afl
http://forum.qmailrocks.org/archive/index.php/
Course if you are running QMR, you might ask there, but by that time we will have found it.
Possibly a bounced mail header.
Nosis| Obnosis | (503)754-4452
PLUG Linux Security Labs 2nd Saturday Each Month@Noon - 3PM
> Subject: Fail Message is Fail Messages for Fail Messages that I Never Failed to Send???
> From: tuna@supertunaman.com
> To: plug-discuss@lists.plug.phoenix.az.us
> Date: Tue, 10 Mar 2009 15:35:45 -0700
>
> This really clubs me in the kneecaps with a concealed-sword cane.
>
> Over the past two days, I have been getting these messages that would
> suggest that I'm sending viagra spam to people and failing at it. I am
> getting dozens of those qmail-send failmails. Some of them are in
> Spanish or German. I have been just marking them as spam so I wouldn't
> see them but THEY'RE JUST TOO MANY, CAPTAIN!!!
>
> I've actually been thinking of writing a little script server-side to
> just archive them and give them to me in a weekly digest, and during bad
> spells like this I could just have it not send them at all.
>
> If plug-discuss doesn't have a better solution, that is.
>
> kthx
> --
> Andrew "Tuna" Harris
> Hacker, Caffeine-Addict
> http://supertunaman.com
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