In Outlook, the Inbox folder is usually found on the same hierarchy level as Calendar, Contacts, etc. On the IMAP server, the Inbox is the root folder of a user, with all other folders such as Calendar, Contacts etc. as subfolders of the Inbox.

The Groupware Client translates these two different concepts and displays the Outlook folders according to the standard Outlook format.

In Outlook, however, it is possible to create subfolders in the Inbox. On the IMAP server, however, there are no differences between subfolders of the Inbox and folders at the same level of the Inbox. If this happens, the groupware client creates a folder called ibx_sub on the IMAP server, and stores all Outlook inbox subfolders inside it.