mail: Ensure proper encoding of the To header

When using the php mail() function, the To: header encoded in the Mail_mime
library was not properly transferred to the $to variable passed to the mail
backend. The mail() function will add its own To: header which will
mimic the received destination address.

This patch ensures that the $to parameter is properly encoded.

include/class.mailer.php

@@ -509,6 +509,8 @@ class Mailer {
 
         //No SMTP or it failed....use php's native mail function.
         $mail = mail::factory('mail');
+        // Ensure the To: header is properly encoded.
+        $to = $headers['To'];
         return PEAR::isError($mail->send($to, $headers, $body))?false:$messageId;
 
     }