mail header Return-Path not taking

[freebie]

Hi,
Does anyone know why the "Return-Path" header might not be taking. All the other headers, such as "Reply-To" and "Content-Type" are working fine. With "Return-Path" it always shows up as [e-mail] instead of "[e-mail]". The reason I need this to work properly is that it's sending a "text message" email to a cellphone, and it seems to display the return-path as the from address, and I would rather it display [e-mail] rather than [e-mail].
Thanks for any suggestions.

[freebie]

I found at that it seems that this either has to be done using php.ini or using the optional 5th parameter of the mail function as such:
mail($to_email, $subject,$message,$mailheaders,"[e-mail]");

using the 5th parameter like this probably only works if sendmail is the MTA.