BATV
also: Bounce Address Tag Validation, BATV signing
BATV (Bounce Address Tag Validation) is an email authentication technique that tags the return path of outgoing mail with a cryptographic signature, allowing the sender to identify and reject bounces from forged messages.
BATV works by modifying the envelope sender (Return-Path) address to include a hash or tag derived from the original sender's domain and a timestamp. When a message bounces, the Mail Delivery Agent (MDA) verifies this tag before returning the bounce to the sender.
If the tag is invalid or missing, the bounce is assumed to have come from a forged message and is silently discarded. This prevents backscatter—unwanted bounce messages caused by spam with forged sender addresses.
For example, instead of using [email protected] as the return path, BATV might transform it to [email protected], where the hash encodes validation data that the receiving MTA can verify.
BATV is less commonly deployed than SPF, DKIM, and DMARC, but remains useful for sites receiving high volumes of bounces from spoofed messages.