Wrong Return-Path

[DecIRC]

The mail my system is sending to my customers are always detected as spam.
The reason is easy to understand

Code:

Return-Path: <webmaster@magog.cqfd.net>
From: webmaster@cqfd.net

magog.cqfd.net is the fqdn of my server.
I'm unable to find where to change the return path to have webmaster@cqfd.net instead of webmaster@magog.cqfd.net

I made a search in /etc and found

Code:

ispcp/fcgi/working/master.php.ini:sendmail_path = "/usr/sbin/sendmail -t -i -f webmaster@magog.cqfd.net"

I have replaced with webmaster@cqfd.net, and then restarted apache.
I have made a search in the iscp database
I have made a search in this forum (searching return-path)

Any idea ?
Thanks