Filtering OutBound SPAM

Randal, Phil prandal at
Wed Feb 4 15:31:25 GMT 2009

Whilst everything comes from the same IP (client's MTA), the Received
headers should have the infected box's IP address.
Give that/those a high score in spamassassin, and tell the client to
clean their infected PCs
Phil Randal | Networks Engineer 
Herefordshire Council | Deputy Chief Executive's Office | I.C.T.
Services Division 
Thorn Office Centre, Rotherwas, Hereford, HR2 6JT 
Tel: 01432 260160 
email: prandal at 

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From: mailscanner-bounces at
[mailto:mailscanner-bounces at] On Behalf Of Eduardo
Sent: 04 February 2009 15:22
To: MailScanner discussion
Subject: OT: Filtering OutBound SPAM

Hi, i've a rare scenario with one of my customers and i though that
someone from here could give me some fresh(?) ideas.

My client has it's own MTA (wich i don't manage, neither have access to
logs, etc) and it sends all outbound traffic to my server that has
(MScanner, SA, clamav, dcc, pyzor, razor, some custom rules, etc).

The problem i've right now is that (i assume) some malware stole valid
user/passwords to authenticate in the smtp server of my client, so tons
of spam are trying to get out to internet through my server.

Althogh all anti-spam stuff seems to work, i need some new
countermeasures to stop this at MailScanner stage (i cant do anything at
MTA level because everything comes from the same ip).

Any idea?

something like my own checksum repository, or url blacklist, or header
authentication matching, etc.

Any help would be appreciated.


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