This is a common issue which happens when using the cPanel username for authenticating on the smtp server. Please use the email username instead and this issue will be resolved.
For more information please check our Mail tutorial:
http://hostlantern.com/clients/knowledgebase.php
Setting up your email is easy when you have the right host by your side. If you need a reliable partner to help you resolve email issues and provide expert support, check out our email hosting services.
