Messages In Gmail Sub Folders Appear as Read

If you use Advanced IMAP Controls from Gmail Labs in addition to Message Filters that move incoming messages from a Gmail inbox into another folder, Postbox may fail to turn the folder bold to indicate the folder has unread messages or the message is already marked as read.

To fix this, log into the Gmail web interface and select Settings and then Forwarding and POP/IMAP and then make sure Auto-Expunge Immediately Update the Server