how change tote castle controlling php mail?

i am controlling php apache linux, sendmail. i php function. email sent, nonetheless tote apache_user@localhostname mail from (example nobody@conniptin.internal) remote mail servers reject since domain doesn't exist (obviously). controlling mail, i force change tote mail from?

edit: i supplement header fourth domain mail() function, changes from domain headers physique message, does change tote mail from.

i force spawning sendmail sendmail -t -odb -oi -frealname@realhost piping email essence it. improved approach?

is there better, simpler, some-more php suitable proceed doing this?

edit: bottom line i should have rtm. interjection answers folks, fifth parameter works well.