diff --git a/data/web/inc/ajax/dns_diagnostics.php b/data/web/inc/ajax/dns_diagnostics.php
index 45ff07e2..dd67dec9 100644
--- a/data/web/inc/ajax/dns_diagnostics.php
+++ b/data/web/inc/ajax/dns_diagnostics.php
@@ -74,7 +74,7 @@ if (!isset($autodiscover_config['sieve'])) {
 
 // Init records array
 $spf_link = '<a href="http://www.openspf.org/SPF_Record_Syntax" target="_blank">SPF Record Syntax</a><br />';
-$dmarc_link = '<a href="http://www.kitterman.com/dmarc/assistant.html" target="_blank">DMARC Assistant</a>';
+$dmarc_link = '<a href="https://www.kitterman.com/dmarc/assistant.html" target="_blank">DMARC Assistant</a>';
 
 $records = array();
 if ($_SESSION['mailcow_cc_role'] == "admin") {