See the GNU General Public License or the Artistic License for more details. Users can create a hierarchy of multiple mailboxes and browse and move messages between them. Messages with MIME attachments can be displayed nicely. Files local to the client browser can be included in composed messages or MIME attached to them.
WING is scalable up to thousands and tens of thousands of users.
This is the only part of WING which requires frame support from the browser. Users can create address books which can be browsed, searched and shared in an ACL controlled manner with chosen lists of other users and groups. WING server nodes can be added or removed transparently and can be taken down for upgrades without affecting user service. There are a few web-based admin tools for querying the status of the WING cluster and its users. In its current state, WING requires many other pieces of software to function.