diff --git a/custom/vendor/PHPMailer.Lite.php b/custom/vendor/PHPMailer.Lite.php
index 8a15dde..925f275 100644
--- a/custom/vendor/PHPMailer.Lite.php
+++ b/custom/vendor/PHPMailer.Lite.php
@@ -709,18 +709,15 @@ class PHPMailerLite
         }
         $tld = substr($url, strpos($url, ".") + 1);
         if ($validate === "is_valid") {
-            $url = $tld;
+            // Just check if the SMTP host is reachable via DNS (A record)
+            // The original check compared SMTP host to MX records which breaks
+            // third-party SMTP services like Mailgun, SendGrid, etc.
+            return checkdnsrr($url, 'A') || checkdnsrr($url, 'AAAA');
         }
         if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $tld, $match)) {
             getmxrr($match['domain'], $mx_details);
             if (is_array($mx_details) && count($mx_details) > 0) {
-                if ($validate === "is_valid") {
-                    if ($url == reset($mx_details)) {
-                        return true;
-                    }
-                } else {
-                    return reset($mx_details);
-                }
+                return reset($mx_details);
             }
         }
         return false;
@@ -961,12 +958,8 @@ class PHPMailerLite
             $rz = false;
         }
         if ($rz) {
-            $rz = false;
-            $check = @fsockopen($domn, 80, $errno, $errstr, 1);
-            if ($check) {
-                $rz = true;
-                @fclose($check);
-            }
+            // Check DNS records instead of port 80 (mail-only subdomains don't have web servers)
+            $rz = (checkdnsrr($domn, 'MX') || checkdnsrr($domn, 'A'));
         }
         if ($rz) {
             $rz = (bool) preg_match('/^(?!(?:(?:\x22?\x5C[\x00-\x7E]\x22?)|(?:\x22?[^\x5C\x22]\x22?)){255,})(?!(?:(?:\x22?\x5C[\x00-\x7E]\x22?)|(?:\x22?[^\x5C\x22]\x22?)){65,}@)(?:(?:[\x21\x23-\x27\x2A\x2B\x2D\x2F-\x39\x3D\x3F\x5E-\x7E]+)|(?:\x22(?:[\x01-\x08\x0B\x0C\x0E-\x1F\x21\x23-\x5B\x5D-\x7F]|(?:\x5C[\x00-\x7F]))*\x22))(?:\.(?:(?:[\x21\x23-\x27\x2A\x2B\x2D\x2F-\x39\x3D\x3F\x5E-\x7E]+)|(?:\x22(?:[\x01-\x08\x0B\x0C\x0E-\x1F\x21\x23-\x5B\x5D-\x7F]|(?:\x5C[\x00-\x7F]))*\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-[a-z0-9]+)*\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-[a-z0-9]+)*)|(?:\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\]))$/iD', $email);