If you're using a custom mail.php script, check the part where the EHLO command is being sent. It may need adjustments, such as sending HELO instead of EHLO, or handling the server's response better.If you're using a custom mail.php script, check the part where the EHLO command is being sent. It may need adjustments, such as sending HELO instead of EHLO, or handling the server's response better.