From OCS Support Wiki

Introduction

This guide will show you how to forward an address on your website to another mailbox.

Setting up Forwarding

NOTE: If you have already setup a mailbox in cPanel, you must delete it first before you forward it elsewhere, or else you'll end up with both a forwarded copy and a local copy, and the mailbox can fill up inadvertently.

• Log into cPanel
• Login to cPanel and click Forwarders under the Mail section
• Click the Add Forwarder button
• On the following form, when asked for the address to forward, put in the e-mail address on your website you wish to forward. Make sure Forward to an e-mail address is selected and enter the destination you want that address forwarded to.
• Click the Add Forwarder button to add the forwarding address

On the form asking for the address and destination e-mail, you can pick more advanced options, including forwarding it to a script or returning a bounce with a specific error message.