Patent ID: 8572190

Claim:
A method of recognizing an incoming email message, received at an email firewall, as being non-SPAM, comprising the steps of: arranging contents of an outgoing email message, received at the email firewall from a private network, into outgoing message fragments, each outgoing message fragment corresponding to a portion of the contents of the outgoing email message; for each outgoing message fragment, creating a stored outgoing message fragment representation of at least a portion of the outgoing message fragment; designating the stored outgoing message fragment representation as corresponding to a non-SPAM message based on the outgoing message fragment originating in an outgoing email message; arranging contents of the incoming email message, received at the email firewall from a public network, into at least one incoming message fragment, each incoming message fragment corresponding to a portion of the contents of the incoming email message; for each incoming message fragment, creating an incoming message fragment representation of at least a portion of the incoming message fragment; comparing each incoming message fragment representation to the stored outgoing message fragment representations to identify matches therebetween, wherein matches indicate a portion of the contents of the outgoing email message in the contents of the incoming email message; and identifying the incoming email message as being non-SPAM in response to the contents of the incoming email message comprising a threshold amount of the contents of the outgoing email message based on the matches between the incoming message fragment representations and the stored outgoing message fragment representations exceeding a pre-defined threshold test.