I'm using my IMAP account to read and manage my mails from different places: e.a. from home and from the office. If I file a mail in a differen folder than the inbox and mark them as unread and connect to your account from an other location this other folder will not be displayed as having unread messages in it (same behavior would be if you sort your mails in different folders on IMAP server). Otherwise you would have to open all your folders to check if there is an unreaded mail in it. Maybe it's possible to add the feature to check for new/unreaded mail in other folders than the inbox. To prevent users that don't need that feature from wasting their bandwidth and time by checking, it would be useful to have the ability of enabling and disabling that functionality like you can enable or disable sharing of a folder.
*** This bug has been marked as a duplicate of 18266 ***
Verified as dup.