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Is there any way to perform SRS, or something similar using Postfix?

When I get a mail from [email protected], I forward it (via a catchall) to [email protected], but GMail is checking SPF, and seeing that my server is not authorized to send mail on behalf of example.org. I'd like to rewrite the sender to something@myserver, while leaving the from as [email protected].

1
  • The install of postsrsd, at least on Debian, is now much simpler than in the older answers below. See for example my answer here: serverfault.com/a/1120558
    – mivk
    Jan 18, 2023 at 17:42

4 Answers 4

8

Here are the steps to install postsrsd from Timo Röhling. These instructions seem to work for many Unix flavors including Ubuntu 14.04.

# Debian/Ubuntu preparations:
sudo apt-get install cmake sysv-rc-conf

# download and compile the software:
cd ~
wget https://github.com/roehling/postsrsd/archive/master.zip
unzip master
cd postsrsd-master/
make
sudo make install

# or alternatively install binary from later Ubuntu repositories
sudo apt-get install postsrsd

# Add postfix configuration parameters for postsrsd:
sudo postconf -e "sender_canonical_maps = tcp:127.0.0.1:10001"
sudo postconf -e "sender_canonical_classes = envelope_sender"
sudo postconf -e "recipient_canonical_maps = tcp:127.0.0.1:10002"
sudo postconf -e "recipient_canonical_classes = envelope_recipient"

# Add SRS daemon to startup (Red Hat 6/CentOS):
sudo chkconfig postsrsd on
# Add SRS daemon to startup (Debian/Ubuntu):
sudo sysv-rc-conf postsrsd on
# Start SRS daemon:
sudo service postsrsd restart
#Reload postfix:
sudo service postfix reload
5
5

There's a 2012 tutorial here on setting up SRS with Postfix on Debian: http://blog.phusion.nl/2012/09/10/mail-in-2012-from-an-admins-perspective/

Here's a 2013 tutorial for Ubuntu: http://www.ameir.net/blog/archives/71-installing-srs-extensions-on-postfix-ubuntudebian.html

1
1

Here are some thoughts, which will require some customization to meet your exact needs. The first thing I found was that Postfix doesn't seem to like doing anything to addresses that are aliases (i.e. virtual_alias_domain/virtual_alias_maps). But that's fine since in reality it doesn't matter what these addresses are called as long as everything gets delivered properly in the end.

So, in Postfix's main.cf, add the following lines:

virtual_mailbox_domains = example.org
# Feel free to give munger a better name, just update master.cf appropriately
virtual_transport = munger:

Next, you need to tell Postfix what munger actually means. Add the following (see pipe(8) for more options). So add the following to master.cf:

munger    unix  -       n       n       -       -       pipe
  flags= user=nobody argv=/usr/bin/redirector

According to the above, anything destined for example.org will get sent to the /usr/bin/redirector program (or whatever you want to call it). For most normal things, you'd need some command line arguments for sender/recipient information (again, pipe(8) has more details) but since the sender and destination addresses are fixed, nothing else is needed on the command line.

Now you just need to write the redirector program. This worked for me:

#!/bin/sh
/usr/sbin/sendmail -bm -f 'something@myserver' '[email protected]'

It's a regular shell script (or your language of choice) so make it as simple or complex as you like.

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  • 1
    This isn't srs, you can't use it for passing bounces back to the origonal sender securely. Sep 9, 2013 at 15:38
-4

You would better forget the whole spf thing and use dkim instead.

Here is a good article describing SPF problems.

3
  • 1
    Try telling that to Google - as it's Gmail doing the checking not the poster. Feb 25, 2010 at 8:26
  • 1
    Google is checking the records that the OP set up.
    – cstamas
    Mar 31, 2010 at 23:30
  • 4
    That article was written in 2004, and some of what it says is no longer true; for example, SPF now has its own DNS record type, per RFC4408. Nearly the whole of the rest of the article boils down to "it breaks simple forwarding" and "its arbitrary rewriting of the envelope-from breaks these other systems which arbitrarily use the envelope-from". The former is true, but a price worth paying, to my mind; the latter is true, and tough - one arbitrary use is not implicitly better than another.
    – MadHatter
    Nov 14, 2010 at 9:56

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