29Mar/110
Catching unsolicited bounces (backscatter) with SpamAssassin
From http://wiki.apache.org/spamassassin/VBounceRuleset
The “Virus Bounce Ruleset” is a SpamAssassin ruleset to catch “backscatter”.
Backscatter is mail you didn’t ask to receive, generated by legitimate, non-spam-sending systems in response to spam.