Detecting bounced messages by Return-Path header

Question

some time ago I saw a question about detecting bounced messages:

I am working on a tool that will be sending bulk messages (not spam :) and I need to add a feature t

Answer 1

The pertinent standard is called VERP, by the way.

You mean bounce+token@yourdomain.com, not just plain bounce@yourdomain.com. The token is what makes it unique!

Postfix will already accept mail for a+something@example.net given a valid address a@example.net as long as you configure the recipient_delimiter in main.cf:

recipient_delimiter = +

There are a few different ways to configure Postfix so that it will deliver the mail to your script AND tell you what the token was. Try this:

1. Create the address bounce@yourdomain.com the same way you create aliases normally in that domain: e.g. a regular alias or a virtual mailbox

2. Create a custom delivery transport in master.cf. ${extension} means that the script will receive whatever came after the + as its first argument, and <username> should the the local uid under which the script should run.

   bounce   unix  -       n       n       -       -       pipe
     flags=R user=<username> argv=/script/which/receives/bounces ${extension}
   

3. Create a transport map if you don't already have one:

   transport_maps = hash:/etc/postfix/transport
   

4. Add the following line in /etc/postfix/transport to direct bounce@yourdomain.com to the new transport you created in master.cf:

   bounce@yourdomain.com    bounce:
   

5. Rebuild the transport map:

   postmap /etc/postfix/transport