For plesk version 10 and above
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1. Log into plesk control panel.
2. Select the particular domain from "Domains" list.
3. Select the "Mail" tab from the window.
4. Select "Create E-mail Address" option.
5. Provide valid username and password.
6. Click on "OK" button.
For plesk version 9
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1. Log into plesk control panel.
2. Select the particular domain from "Domains" list.
3. Select the option "Create Mail Account" from "Mail" tab.
4. Provide valid user name and password.
5. Click on "Finish" button.