For Plesk version 11
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1. Log into Plesk control panel.
2. Select the desired domain from "Domains" list.
3. Click on "Open in Control Panel" option under "Hosting" section.
4. Select "Change Settings" option from "Mail" tab.
5. Uncheck the box "Activate mail service on domain".
6. Click "OK" button.
For Plesk version 10
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1. Log into Plesk control panel.
2. Select the desired domain from "Domains" list.
3. Select "Change Settings" option from "Mail" tab.
4. Uncheck the box "Activate mail service on domain".
5. Click "OK" button.
For Plesk version 9
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1. Log into Plesk control panel.
2. Select the desired domain from "Domains" list.
3. Select "Mail Accounts" option from "Mails" section.
4. Select "Mail Settings" options from "Tools" section.
5. Uncheck the box "Activate mail service on domain".
6. Click "OK" button.