Mailing List Message #99534
From: Nicolas Hatier <>
Subject: Re: Released: ListBackscatter v1.0, to reduce backscatter caused by the LIST module
Date: Wed, 24 Feb 2010 12:45:24 -0500
To: CommuniGate Pro Discussions <>

As far as I now, the LIST module never replies on the SMTP channel, for instance when a non-subscriber tries to post to a subscribers-only list. This is why this filter can be needed.

The filter will actively reject (not bounce) non-subscribers messages, and spurious unsubscribe attempts (unsubscribe requests coming from non-subscribers). The filter checks the list settings first and will of course allow non-subscribers messages on an open list.

Nicolas Hatier

On 2010-02-24 12:29, Massimo Bolzoni wrote:

question: also using syncronous mode the list module reply back NOT on the smtp channel? I got it correct?



Il giorno 24/feb/10, alle ore 18:15, Nicolas Hatier ha scritto:

This new filter reduces the backscatter caused by the Communigate Pro LIST module.

The CGP LIST module processes the received messages only after it has been accepted at SMTP level. When spammers attack a server, they may attack a list address, and this will likely cause backscatter (bounces) to the random third-party addresses used by the spammer. This may even get your server listed in a few DNSBL such as SpamCop's or's.

The List Backscatter Filter reduces the avoidable bounces by matching the message sender with the subscriber list, and rejecting unauthorized addresses at SMTP level, with the help of CGP synchronous rules (CGP 5.1+)

Future versions may be enhanced with new verifications for other causes of backscatter. Suggestions / comments welcome.

Best regards
Nicolas Hatier


Nicolas Hatier, ing. <>
Niversoft idées logicielles -

Massimo Bolzoni - Solution Architect
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Niversoft idées logicielles -

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