A good way to keep your database clean and focus on active contacts is to delete or archive them.
Sign into your backoffice at https://www.enagicwebsystem.com/backoffice.php
On the left navigation column, click on Marketing System > Contact Manager.
Right click on the contact's name. Select Delete or Archive the contact.
Note: Once you Delete it there's no way to recover it, which means that you will definitively take it off your list.
If you just Archive your contacts you will be able to retrieve their information later by clicking on "view archived contacts" at the bottom of your contacts list.