I have been testing MDaemon & other email server software in order to put them into production in our office.

MDaemon has two ways of sharing emails : Public folders & shared folders with their own ACLs. In public folders the flags can be either per user or shared flags with other users. If the flags are shared with other users, then the Read, Unread, Replied, Forwarded, etc. all status are shared with other users, this way one can know which emails have been replied or forwarded. However if the Public Folders are configured with Per User IMAP flag settings, then every user does get to know which emails are new and unread by him, but it does not reflect whether a particular email has been replied or forwarded by any of his colleague. What I am looking is for a situation where all flag status are shared between the users except for the read / unread status. This way every user will have a clear picture of the conversation as well as what mails are new to him. This is a feature that works well with other mail servers such as Axigen & Desknow, where all flags are shared except for read unread status which is configured on a per user basis.