Is there any way to perform SRS, or something similar using Postfix?
When I get a mail from user@example.org, I forward it (via a catchall) to something@gmail.com, 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 user@example.org.
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
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
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' 'something@gmail.com'
It's a regular shell script (or your language of choice) so make it as simple or complex as you like.
You would better forget the whole spf thing and use dkim instead.
