1. Log in as a user with your full username and password into your Smartermail web mail via the link
http://mail.domain.com (Domain.com represents your domain name)
2. Then go to Settings tab and then click on Account Settings on left panel.
3. Then go to right interface and click on the Forwarding tab and enter the email account for receiving your forwarded emails. Check on the box for "Enable deletion of messages on forward" IF you would like to have the email to be deleted from your mailbox after being forwarded.
Note :Make sure your forwarding email address is not the email accounts from free email services such as Gmail, Hotmail, Yahoo and etc