UniStream supports sending email via a encrypted -SSL- email server such as Gmail, Hotmail, Yahoo, etc.
Please take in mind that some external email servers such as Gmail have security protection that is set as default to "Do not allow external or 3rd party application connect to your account". If this option is enable, Gmail will not allow the UniStream to connect to your account and send email in your behave. So Please make sure this option is disabled.
I know that on Gmail you can find it as follow: