how to bounce mail

rfc 2821 (the successor to the venerable rfc 821, the original smtp standard specification) is quite clear in section 6.1 about where to report delivery failures after your smtp server has accepted the message: The recipient of this notification MUST be the address from the envelope return path (or the Return-Path: line).

(and note that Return-Path is not a header sent to you -- outgoing SMTP servers SHOULD NOT add one according to section 4.4 of the same specification.)

perhaps there should be a bounces-to-wrong-address.rfc-ignorant.org. perhaps a uses-braindead-virus-scanner.rfc-ignorant.org would be useful, too.