[Evolution-hackers] What is the rules for vfolder/unmatched?

[Gilbert Fang <gilbert fang sun com>]

Hi, all

  I am using evolution 1.3.99. 
  I created some vfolder for my imap mail account. In my imap account,
there are some other imap folder other than inbox. But all my vfolder's
source is the inbox. 
  Then I find there are many items appearing in the unmatched vfolder,
which seems a built-in vfolder. But I wonder what is the source for the
unmatched vfolder? the all folder of my imap account, or only the all
the others vfolders' source folder, or something else?

  I am really confused by it?

Best regards
Gilbert