All email functions can be managed through the eXtend Control Panel > Email Forwarding, in the 'Email Configuration' section. 

The top half of the page allows you to add a new forwarding address and the bottom half lists addresses you have already setup, these can then be edited. 

Each email address can be forwarded to up to ten other addresses. If you need to forward to more than this a mailing list may be more suitable - these support up to 2500 recipients.