1. Log in to Plesk.
2. click on Mail.
3. On the mail page, click on the e-mail address for which you want to enable a forwarder.
4. Click on the Forwarding icon.
5. Select the checkbox of the "Switch on mail forwarding".
6. After that type the email address to which you want to forward your messages in the "Forward incoming messages" text box.
7. Click on the OK icon.
If you do not want to use the email forwarding then please refer the below steps to disable email forwarding:
1. Log in to Plesk.
2. Click on Mail.
3. On the mail page click on the e-mail address for which you want to disable a forwarder.
4. Click on the Forwarding tab.
5. Uncheck the "Switch on mail forwarding".
6. Click on the OK icon.
In this way, you can enable and disable the email forwarding in the Plesk.