diff --git a/Application/Controller/Admin/SmtpChecker.php b/Application/Controller/Admin/SmtpChecker.php
index 6e5a969..1ba08c7 100644
--- a/Application/Controller/Admin/SmtpChecker.php
+++ b/Application/Controller/Admin/SmtpChecker.php
@@ -123,7 +123,7 @@ class SmtpChecker extends AdminDetailsController
     {
         $this->action = __FUNCTION__;
         Assert::that(
-            ($this->smtp = new Net_SMTP($this->host, $this->port)),
+            ($this->smtp = new Net_SMTP($this->host, $this->port, $_SERVER['HTTP_HOST'])),
             Registry::getLang()->translateString('D3_MAILCHECKER_SMTPCHECK_INSTANCE')
         )->isInstanceOf(
             Net_SMTP::class,