Using watermark to fight spam backscatter

[Edward Prendergast]

Hi,

More and more of our users are receiving large quantities of spam backscatter. One received 200 messages this week. 

I've been investigating various options (Postfix rules: http://tinyurl.com/2vdes7, BATV: http://mipassoc.org/batv/) but the easiest to implement seems to be MailScanner's watermarking, especially as my system already uses watermarking (we have a postfix + mailscanner gateway in front of a cPanel exim + mailscanner box).

Watermarking is already successfully implemented and working properly between the two machines. I've altered this setting for testing:

Treat Invalid Watermarks With No Sender as Spam = 0.1

But after changing this and checking the incoming mail I've noticed a lot of backscatter doesn't come with From: <> but rather real e-mail addresses (e.g. MAILER-DAEMON at mx-8.masterhost.ru). Is this the right area to be looking in? Could this be modified, or should I be using some other feature to help cut down on this?

Thanks,
Edward


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