You could do the ini set inside of the Universal Email code that is on the contact us page. You can put it in just before the UE setting of the recipient to the globals value, here is what the code chunk should look like:
<?php
if ((($_SERVER["REQUEST_METHOD"] == "POST") && (isset($_SERVER["HTTP_REFERER"]) && strpos(urldecode($_SERVER["HTTP_REFERER"]), urldecode($_SERVER["SERVER_NAME"].$_SERVER["PHP_SELF"])) > 0) && isset($_POST))) {
//WA Universal Email object="mail"
//Send Loop Once Per Entry
ini_set("sendmail_from", "".((isset($_POST["Email_address"]))?$_POST["Email_address"]:"") ."");
$RecipientEmail = "".($WAGLOBAL_Contact_Email_To) ."";include("WA_Universal_Email/WAUE_contact_1.php");
//Send Mail All Entries
if ("index.php"!="") {
header("Location: thankyou.php");
}
}
?>
To modify the mail call you need to edit the WA_Universal_Email > mail_PHP.php file. In here find do a search for the line that stars like this:
$mailObj = mail($mailTo,$mailSubject,$mailContent,$mailHeader
Update this line of code to look like this:
$mailObj = mail($mailTo,$mailSubject,$mailContent,$mailHeader, "-f" . "".((isset($_POST["Email_address"]))?$_POST["Email_address"]:"") .""));
I think this will meet the needs of the host to set the send mail from value and add in the -f parameter into the mail call.