s/qmail:srsreverse

Section: User Commands (1)
Index Return to Main Contents

NAME

srsreverse - reconstruct the original address from its SRS extension and forward bounce mail

SYNOPSIS

in .qmail: |srsreverse

DESCRIPTION

Upon reception by qmail-smtpd, qmail-local may feed a locally delivered bounce email through srsrevers in order to reconstruct the original sender from the received SRS address provided in the local part and to forward the bounce mail to its original address.

SRS DOMAINS

In order to accept emails for SRS modified return addresses, you need to setup those in rcpthosts. If your domain is example.com in rcpthosts you probably want to set up additionally srs.example.com. However, .example.com would be fine as well.

VIRTUAL SRS USER

SRS can facilitate a virtual user typically named srs and thus requires an entry like srs.example.com:srs in virtualdomains.

DOT QMAIL

srsreverse is called from a dot-qmail file which could be SQMAIL/alias/.qmail-srs-default.

CONTROL FILES

srsreverse reads the control file virtualdomains to exfiltrate the (virtual) SRS user name for the received domain, if given. With the evaluated srsdomain, srsrevers fetches the SRS secret from srsdomains in order to validate the SRS bounce address.

ENVIRONMENT VARIABLES

srsrverse reads the environment variables DTLINE, HOST, and RECIPIENTS. HOST is used to determine the srsdomain. The forwarding bounce address is reconstructed from the local part of RECIPIENTS.

VERP

The Sender Rewriting Scheme SRS can be considered as tailored form of VERP: Variable Envelope Return Path. The chosen primary delimiter = is recognized by qmail-smtpd's recipient extension.

REFERENCE

srsreverse was initially based on srs2.c from libsrs2, but was replaced in s/qmail-4.4 by a genuine implementation.

This document was created by man2html, using the manual pages.
Time: 10:54:32 GMT, October 05, 2026