WebMail gives you two methods to delete groups.
The first method is to use the edit groups function.
The second method is to use the "Delete" link on the group viewing page. To use this method, click the "Groups" link on the WebMail main page. Select a group by clicking its name. When the group viewing page is displayed, click the "Delete group" link to permanently delete the group.
Once deleted, a group cannot be recovered.