Usermin - How create on Inbox, some subfolders ?

Dear team,

Usermin - How create on Inbox, some subfolders to manage the messages (as squirrelmail)?

For example:

Inbox
--- Inbox 2009
------ Profesional
------ Advertising
------ Real estate
--- Inbox 2008
------ Archives 1T08
------ Archives 2T08

What's the difference between composite, virtual and traditional folder ?
I don't find it on the documentation

Thank you

Status: 
Closed (fixed)