The All messages page contains the messages sent and received by everyone in a project. Only users with View all correspondence permission can access this page.
Once a user gains the permission, the All messages item in the project level menu will be unlocked.
The All messages page is simple. It has a search bar that will let you find a message by typing its name, a word or group of words in its message body, sender, recipient, or an attached article's name.
Beyond that, we have the list of all messages with information about their senders, recipients, the date they were sent, and the message body.
Aside from that, there's nothing else you can do here. You can't edit or delete these messages, etc. This only serves as an additional way of monitoring what users are doing in the project.