diff --git a/data/web/inc/ajax/dns_diagnostics.php b/data/web/inc/ajax/dns_diagnostics.php
index 4744023e..23d99041 100644
--- a/data/web/inc/ajax/dns_diagnostics.php
+++ b/data/web/inc/ajax/dns_diagnostics.php
@@ -13,22 +13,22 @@ $domains = mailbox('get', 'domains');
 foreach(mailbox('get', 'domains') as $dn) {
   $domains = array_merge($domains, mailbox('get', 'alias_domains', $dn));
 }
-      $domain = $_GET['domain'];
 
-// if (isset($_GET['domain'])) {
-  // if (is_valid_domain_name($_GET['domain'])) {
-    // if (in_array($_GET['domain'], $domains)) {
-    // }
-    // else {
-      // echo "No such domain in context";
-      // die();
-    // }
-  // }
-  // else {
-    // echo "Invalid domain name";
-    // die();
-  // }
-// }
+if (isset($_GET['domain'])) {
+  if (is_valid_domain_name($_GET['domain'])) {
+    if (in_array($_GET['domain'], $domains)) {
+      $domain = $_GET['domain'];
+    }
+    else {
+      echo "No such domain in context";
+      die();
+    }
+  }
+  else {
+    echo "Invalid domain name";
+    die();
+  }
+}
 
 $ch = curl_init('http://ip4.mailcow.email');
 curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);