At my last job we had several shared IMAP mailboxes. The workflow that we used that worked fairly well was to have a sub-folder for each user. When a new mail

At my last job we had several shared IMAP mailboxes. The workflow that we used that worked fairly well was to have a sub-folder for each user. When a new mail came in, you'd first move it into your folder, then handle the email. This worked really well for us, but I think the biggest inbox only had a dozen users.