1. Click on the Mail tab 
2. Select an e-mail address
3. Click on the Forwarding tab 
4. Click on the "Switch on mail forwarding" if it is not
switched on already
5. Type in an e-mail address you want to forward e-mails to
6. Click the OK button.
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How to set up E-mail Forwarding - Plesk 10
Parallels Plesk Panel is a web hosting control panel that helps you manage your hosting account and assists you in creating web sites, managing e-mail addresses, & deploying applications to a server.
Plesk 10 is available on HostGator VPS, Windows Dedicated Servers, and Windows Shared Hosting.