VERP (Variable Envelope Return Path)

VERP (Variable Envelope Return Path) encodes each mailing-list subscriber's own address into the envelope sender of the copy they're sent, so a later bounce is self-identifying instead of generic. AdminKit's guide to email bounces and backscatter explains how the envelope sender normally routes a failed delivery back to its source.

By AdminKit team, Netbase JSC · Updated November 2, 2026

See how a bounce's envelope sender normally routes it back -- VERP applies the same idea per subscriber

VERP (Variable Envelope Return Path) is a mailing-list convention that rewrites the envelope sender of each individual copy of a message to encode the recipient it was sent to, for example rewriting [email protected] into [email protected] for one subscriber’s copy. If that copy later bounces, the DSN lands on an address that already names the failing subscriber, so list software can identify and unsubscribe a dead address without parsing the bounce body at all. Exim’s own specification documents VERP support via its return_path transport option, crediting the original mechanism description; Postfix and Mailman implement equivalent support. VERP is a widely deployed MTA convention rather than an IETF standard — unlike the RFC 3464 DSN format it relies on, no RFC defines its address-encoding syntax.