To have the checkboxes show up in the webmail interface, follow the steps below. Once completed, there will be a checkbox in front of each email in all of your folders.
1) Once you are logged into the webmail interface hove your mouse pointed over the "Action" link in the upper left-side of the email window. A menu will appear. Select the "Manage User Options" from the list.
2) Select the "Viewing Messages" tab. Click the checkbox labeled "Enable Selection Checkbox in Message List". Click "Save".