Removing users
When users are no longer working on your domain, you can remove their mailbox and service accounts to conserve resources and maintain security.
Note: A special alias called site_blackhole is automatically created when the domain is created. It is not shown in the list of aliases and its only purpose is to act as a repository for all garbage email.
When a user with an alias is removed, the alias can still remain (as it may be referenced by other aliases), but the target user name is replaced by site_blackhole. When an email message is sent to this alias, it will go to site_blackhole. Therefore, when you delete a user, you will see the alias set to site_blackhole.
To remove a user from a domain:delete
Click the Shortcuts tab on the Home page.
In the shortcuts area, click Manage Users (Users section).
On the Manage Users list, locate the user you want to remove, then in the Actions column, click . The confirmation window is displayed.
Verify that you want to remove the user, and then click OK.