exec'ing sendmail?

Hi, I am experiencing problems with an email distribution utility using the mail function, the 'Return-path' header that I specify gets overwritten by sendmail. I write: Return-Path: <accounts@talismanmarketing.co.uk>\n but sendmail re-writes this as: Return-Path: <nobody@vweb9.hiway.co.uk> My plan is to exec sendmail and use the -f flag to specify a return-path, I can do this from the command line but I am unsure how to go about doing this from within php basically what are the principals of using the exec function, specifically with sendmail and do I have to close the process after each mail that's sent. Many thanks Kevin Price-Ward tmx newmedia -----------------