$_POST['s_smtp'] is a string, not an int.
@ -263,7 +263,7 @@ $smtp_OK = true;
if (empty($_POST['s_smtp'])) {
$set['smtp'] = 0;
$set['use_mailgun'] = 0;
} elseif ($_POST['s_smtp'] === 1) {
} elseif ($_POST['s_smtp'] == 1) {
$set['smtp'] = 1;
} else {