How to Remove/Delete an Email Account in Plesk?
Because they allow customers to set up and maintain several email accounts for their domain, custom emails are a valuable Web Hosting feature. Plesk is only one type of control panel that makes it all possible. Even email accounts may be deleted or removed using Plesk in a few easy steps.
To Remove an Email Account
1. Log in to your Plesk account.
2. Click the Mail option from the navigation menu.
The list of active email accounts on Plesk will appear.
3. Select/tick the box beside the email account/accounts you wish to remove.
4. Click the Remove button.

A pop-up window will appear asking for your confirmation.
5. Click on Yes.

That is all it will take to remove or delete email accounts with Plesk.