I have consulted the manuals and I feel the code follows what they say.
HEre it is:
$referral_body = "<html><head></head><body>";
$referral_body .= "$firstname $lastname has sent you a message about url.com: <br>$pers_messg <br><hr> ";
$referral_body .= "<p align='center'><font face='Arial' size='2'><a href='http://www.url.com'>";
$referral_body .= "Click here to visit url.com</a></font></p>";
$referral_body .= "</body> </html>";
$header = "MIME-Version: 1.0\r\n";
$header .= "Content-type: text/html; charset=iso-8859-1\r\n";
$header .= "From: $firstname $lastname <$email>\r\n";
$header .= "Reply-to: $firstname $lastname <$email>\r\n";
$headers = "From:$email,nReply-to:$email";
//Generate Email to Client
$subject = "Please visit url.com";
mail($friend_emails, $subject, $referral_body, $header,"-f$email");
I receive the above back as text, not HTML code