diff --git a/data/web/inc/ajax/transport_check.php b/data/web/inc/ajax/transport_check.php
index cbf253a9..e956f4f2 100644
--- a/data/web/inc/ajax/transport_check.php
+++ b/data/web/inc/ajax/transport_check.php
@@ -58,6 +58,9 @@ if (isset($_SESSION['mailcow_cc_role']) && $_SESSION['mailcow_cc_role'] == "admi
       )
     );
     $mail->SMTPDebug = 3;
+    if ($port == 465) {
+      $mail->SMTPSecure = "ssl";
+    }
     $mail->Debugoutput = function($str, $level) {
       foreach(preg_split("/((\r?\n)|(\r\n?)|\n)/", $str) as $line){
         if (empty($line)) { continue; }