diff --git a/dns.php b/dns.php
index 595ea01..7639047 100644
--- a/dns.php
+++ b/dns.php
@@ -25,6 +25,7 @@ $data    = json_decode($json, true);
 
 function send_mail($subject, $text) {
   global $mg;
+  global $mailgunDomain;
   $mg->messages()->send($mailgunDomain, [
     'from'    => $mailFrom,
     'to'      => $mailTo,