WA_Globals.php file 
OK, so you are using the Contact Form solution pack then? this detail makes a bit of a difference.
in the WA_UniversalEmail/mail_PHP.php file, find the following line:
php:
$mailObj = mail($mailTo,$mailSubject,$mailContent,$mailHeader);
and change it to:
php:
$mailObj = mail($mailTo,$mailSubject,$mailContent,$mailHeader,"-f<youremail@yourdomain.com>");
where <youremail@yourdomain.com> is a valid email address for your domain
if ti is still not working, edit the WA_UniversalEail/
WAUE_contact_1.php file, change:
php:
$MailFrom = "".((isset($_POST["Email_address"]))?$_POST["Email_address"]:"") ."";
to:
php:
$MailFrom = "<youremail@yourdomain.com>";
