How to rewrite headers in outgoing mail messages

As a workaround, use Postfix header_checks:

1. Connect to the server via SSH

2. Add a header_checks entry to the /etc/postfix/main.cf configuration file (the file specified will contain regular expressions for the rewriting):

   # postconf -e "header_checks = pcre:/etc/postfix/header_checks"

3. If the file /etc/postfix/header_checks does not exist, create it:

   # [ ! -f /etc/postfix/header_checks ] && >/etc/postfix/header_checks

4. Modify the /etc/postfix/header_checks file:

   • For example, to rewrite all headers with From: [email protected] to From: "Mailer-Daemon at server.example.com" <[email protected]> , add the following line to the end of the file:

     /^From:[email protected]/ REPLACE From: "Mailer-Daemon at server.example.com" [email protected]

   • To hide server IP address from headers:

     /^Received:s+.*/ IGNORE

     Note: For more information on regular expressions, refer to the PCRE documentation by php.net .

   • To change Message-ID:

     /Message-Id:s+<(.*?)@server.example.com>/ REPLACE Message-Id: [email protected]

5. Reload Postfix to apply the enabled header_checks:

   # service postfix reload

If a regular expression was applied to the mail message, a similar line will be appended to the /var/log/maillog log file:

server postfix/cleanup[21124]: E5CD0225EF9: replace: header From: [email protected] (Mail Delivery System) from local; from=<> to= [email protected]: From: "Mailer-Daemon at server.example.com" [email protected]

Note: For more information on header_checks feature in Postfix, refer to the Postfix documentation .