I think Thunderbird is an excellent mail client -particularly for Macs - for users on Google Apps. When setting it up for a user, I found that I was getting an error that the folder didn't exist whenever a user would try to view the data in one of the inbox's subfolders. The error looks like this:
But then I found this solution:
In short, Thunderbird is looking for a subfiolder of INBOX - but gmail's folder's when imported from Exchange may often be Inbox. So you need to rename inbox portion of the label to be INBOX. So you'd need to change this:
to this:
