Shared Folders and Bulletin Boards
The Cyrus IMAP server is unique in its capability to make a mailing list available to many users via the IMAP protocol alone. Cyrus accomplishes that feat with shared folders and bulletin boards.
Shared folders and bulletin boards are ordinary Cyrus mailboxes with ACLs that allow more than one user access to the mailbox. There is really not much difference between shared folders and bulletin boards: they are both Cyrus mailboxes, and both allow users other than the mailbox owner to access the mailbox with the permissions defined in the mailbox’s ACL.
When a Cyrus mailbox is referred to as a shared folder, it generally means that it is a mailbox owned by an individual user who wants to allow other users access to the mailbox. An additional feature of a shared folder is that, other than the “read” flag, it does not retain message state information that is unique per user. Message information like deleted or important is global to all users. That feature could be useful if it is desirable to preserve state information across accesses by different users. If you use a shared folder for a group of users, such as a Helpdesk, chances are you will want to preserve the seen and answered states across sessions, to provide a sort of work flow for the Helpdesk employees.
A bulletin board is a Cyrus mailbox that is owned by the system, rather than by an individual user. Bulletin boards are generally used when it is desirable to maintain a per-user seen state. ...