ACTIVATE
If you have previously disabled mail on the domain but would like Plesk to start managing this again, you need to do the following:
1. Log into Plesk
2. Click on the domain from the domains list and open its control panel.
3. Click on the "Mail" tab
4. Click on the "Settings/Change Settings" tab/button
5. Check the box for "Activate mail service on domain" and click OK
DEACTIVATE
If you require the use of a 3rd party/external email server and do not require Plesk to handle your mail you can deactivate it by doing the followng:
1. Log into Plesk
2. Click on the domain from the domains list and open its control panel.
3. Click on the "Mail" tab
4. Click on the "Settings/Change Settings" tab/button
5. Unheck the box for "Activate mail service on domain" and click OK
