php mail() -f additional_parameters does nothing

I've spent the last couple of hours google'ing and trying all sorts of test to
try and set up a bounce address hander for the php mail function.
No mater what i try the -f 5th mail() parameter does nothing.

Using this:

PHP:

<?php
    $mail_to = "bad.user@domain.com";
    $mail_subject = "Subject";
    $mail_message = "Message";
    $mail_headers = 'From: support@mydomain.com' . "\r\n";

    mail($mail_to, $mail_subject, $mail_message, $mail_headers, "-fbounce@mydomain.com");
?>


Even setting:

/etc/mail/trusted-users

to:
apache, nobody, mywwwusr
and without (empty as default)

No matter what I try, the return header in the e-mail always bounces back
to the "From", not the -f bounce user, on good e-mails has the "From", not -f

I've looked through the Exim consider, nothing stands out, i even changed
the -f option there.. (affects outlook comment) nothing... and changed it back.

my php.ini is set to default path:

sendmail_path = "/usr/sbin/sendmail -t -i"


I've got my own server, so it's not an webhoster issue.

I'd like to know how i can tell all mails i send from mail() where to bounce back.

I even tried setting the "Errors-To" (which isn't recommended in the RFC), it's set in the headers,
does nothing... everything still comes back to the "From" sender.

Any pointers on what is preventing this would be great.

 

doesn't anyone have a clue on the above?