1. Login to the user web mail application.
2. Hover to the top and click on the "Settings" option that is with a gear like icon.
3. You'll see a drop down appears. Hover over to "Preferences"
4. Click on "Mail" option.
5. Click on "Deleting and Moving Messages" option.
6. Tick on the check box of"Move deleted messages to your Trash mailbox instead of marking them as deleted in the current mailbox?" and click "'Save"