The MailCOPA multi user email client can share folders between users. A great feature so you can share messages between users on your system without having to compromise your security.
If the user you are sharing a folder with is also logged in to the MailCOPA email software on another machine then you will see their changes to messages happen live in the shared folder. For example if the other user deletes a message, you will see it disappear from the folder on your machine.
Other MailCOPA email software users can even set their own preferences on the shared folder. For example, the folder owner may like to display their email by date received. A sharer may prefer to have their folder sorted by From address, and displaying different fields.
John's Folder List
Marks' Folder List