If you wish to close down an email account permanently, you can delete the account. Deletion of an email account would mean that
- the user will not be able to access the account any more
- all existing emails that have been sent to the account will be deleted
To delete an email account,
- Go to Mail >> Manage Users / Accounts in your control panel.
- Locate the account that you wish to delete from the list, and select the check-box before it. You can select multiple accounts for deletion at the same time.
- Click on Delete.
It is important to note that once you have deleted a user account, it can not be restored at all. If you wish to re-enable the user, you would have to create a new user account with that address.