srsfilter - in dot-qmail filter messages using SRS

in .qmail-srs-default: | /bin/srsfilter

For each email message it processes, srsfilter validates the address in sender before sending it to a mail delivery agent like qmail-inject(8), sendmail(1). srsfilter uses Sender Rewriting Scheme (SRS) to reject (or filter) any incoming bounce messages which are not legitimate responses. The criteria is simply: any incoming messages with an empty envelope sender which go to my main email address must be spam. Real bounces will go to an SRS address instead, and will then be forwarded to a real address. srsfilter rewrites To header with the SRS decoded address. It only accepts messages from null-sender, Return-Path:<>. srsfilter discards double and triple bounces. It also rejects messages without body.

srsfilter is not needed when the MTA can decode SRS addresses. This is the case in a MTA like the indimail-mta, which have programs that can fully rewrite SRS address back to the original sender address like the following programs autoresponder(1), qmail-send(8), qmta-send(8), slowq-send(8), qmail-smtpd(8).

srs(1), qmail-inject(8), sendmail(1) indimail-srs(5),