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Bounce Address Tag Validation (BATV)

Spammers can forge the sender address to look like a legitimate third party email address. The real address then receives bounce backs such as none delivery reports. In this situation, the spammer, in a very clever and effective manner, offloads the entire processing load to the real and innocent end user’s email server. They also leave the end user’s confused and left with a job clearing up none delivery reports and determining why they have received these bounce back messages.

A anti-spam security solution can block illegal bounce back messages. It does this by determining that the original email did was never initiated from the organisation internal network or any of its domains, and therefore an anti-spam filtering device can identify and block them.

This is done by marking each outbound email message with a key and when the bounce back arrives, the anti-spam proxy solution will identify that the key is either present or is not present. If the key is not present then the anti-spam proxy solution knows it is not a valid bounce back and drops the email.

This feature is known as Bounce Address Tag Validation (BATV).

Further Reading

Wikipedia's guide to BATV