We use Postfix to send emails from Java (Tomcat). We want to give each outgoing message a unique Return-Path header, so that our system automatically can register bounced email addresses.
For example, when I send an email to firstname.lastname@example.org I want to use a Return-Path as email@example.com. And when I send an email to firstname.lastname@example.org I want to use a Return-Path as email@example.com.
I set the unique Return-Path header in the email in Java, before passing it on to Postfix through an SMTP connection. I have logged the outgoing message, and it has the correct (unique) "Return-Path" address.
However, when the email arrives to the recipient the Return-Path is set as firstname.lastname@example.org. This is the email address used in From. It seems that Postfix automatically resets our custom Return-Path header with the From header.
I believe this is in line with the SMTP guidelines, when an SMTP server gateway sends an email it should reset the Return-Path header.
How can I configure Postfix so that it does NOT change the Return-Path header for my own emails?