Anyone else having problems related to the php sendmail bug reported here:
http://bugs.php.net/bug.php?id=28976

Apparently it's been reported that in some versions of php, the sendmail functions will send the "Return-Path" that is described in the php.ini file regardless of the path that is provided in the header sent with the mail() function.

I noticed the problem and hostony support is working to help me. It may be different on the various hostony servers, but the one I'm using uses:
Return-path: <nobody@server26.fastbighost.com>
regardless of what I pass in the header when I make the call to mail(...)