[PHP-INSTALL] Please help , qmail with php problem , mail() can't send out email

[info]

I have install qmail in new server , but i get one error from php mail()   this is error i get   Fatal error: Call to undefined function:  mail() in /home/cuser/public_html/mail.php on line 2   mail.php like this <?php mail("[EMAIL PROTECTED]", "My Subject", "Line 1\nLine 2\nLine 3"); ?>   I can't get fix yet.   any one can help me ? i have setup a link to sendmail path , and recompile php , not work.   please help.   Thanks.