I hacked up such a thing in Postfix once.

Postfix itself has no native support for doing any routing based on
source info; neither source interface, nor source IP address, nor
source envelope data (MAIL FROM: in the SMTP dialogue), nor From:
header.

I got a requirement to do this (along with a noisome collection of
other hard requirements). To meet the needs I was already doing
content filtering. I actually (for other reasons, different policies
required based on different incoming interfaces) ran multiple
postfix installs, but the exact same trick would have worked using
Postfix's content-filtering hook with an SMTP proxy. What I did for
source-based routing was to conditionally rewrite the RCPT TO,
depending on what I'd seen in the MAIL FROM. If the MAIL FROM
matched a short list of addrs I wanted to handle bizarrely, I
rewrote the RCPT TO into XXXXXXother.domain, where XXXXXX was the
base64 encoding of the original RCPT TO, and other.domain was a
special reserved domain (from RFC 2606[1]). Then I used a transport
table entry for that domain to route to a pipe transport, with a
script that did the special funky weirdness I needed.

Since what you fundamentally require is to have Postfix send using a
different routing depending on sender addr, you'd need two postfix
installs, one configured with each destination routing; you'd always
inject into one by default, and the content filtering proxy could
redirect into a pipe transport that then undid the thagomizing of
the RCPT TO, and forwarded it on to the other postfix install for
delivery.

I used this trick rather than actually having the proxy do the full
handling, because I found it easier to avoid any variations in the
SMTP proxy dialogue; this was a thin proxy, it actually didn't talk
the SMTP protocol itself at all, it just passed it back and forth
between the Postfix smtp and smtpd, and sometimes modified things in
passing.

This trick is applicable only if the proportion (or absolute
volume) of messages that need this diverting is very small; the
handling of such a message is enormously more expensive than the
normal flow. It's satisfactory for exceptions, it's not satisfactory
for large volume email handling.

-Bennett

[1] <URL:http://www.ietf.org/rfc/rfc2606.txt>

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see http://www.gnupg.org

iD8DBQE8+3Q8HZWg9mCTffwRAh1AAJwM6k1NbD9mNoD3970Rs573IkkQTgCdGSJM
JIm4gFjzIvdgh+ajt0zgbyg=
=uM/T
-----END PGP SIGNATURE-----

-
To unsubscribe, send mail to majordomopostfix.org with content
(not subject): unsubscribe postfix-users

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]