[Dovecot] Shared folders

[Неворотин Вадим]

I need to create a shared folder (mailbox for group mailing list) with
access of several accounts to it. But all peoples with access to this
mailbox should be able to work with this folder absolutely in the same way,
as with local mailbox. Each user should be able to delete emails and mark it
as readed. But this changes must be only for one user, not for others. For
example user1 and user2 have access to folder Trades. There is a new
incoming mail. User1 read it and delete. But in user2's client this mail
must be not readed and not deleted. So there should be only one copy of a
email (in group mailbox), but state (unreaded|readed|deleted) of this email
shoud be different for each user.
Can I do this with dovecot? Yes, I know that I can send a copy of group
letter to each user's mailbox, but unfortunately I has a lot of groups and
very big letters, so I can't duplicate each letter to many mailboxes. The
purpose is to story only one instance of each letter, but to allow users to
work with it like with their own letters. Now I use Maildir++ mailboxes.