Queries retrieve messages that match criteria at the time they're run. Since new messages come into the database independently of the user interface, it is possible to explicitly run again the query and have those new messages added to the current list. This is done with the
command or the F5 key. Note that messages in the current list that no longer match the query are not removed from the list.Built-in selections "New->All" and "Current->All" can also be automatically and periodically refreshed based on the setting on a Preferences parameter (Check new mail every X minutes). When this parameter is set and new messages are available, an icon with a number of messages gets displayed in a button at the bottom right in the status bar and a message "New mail is availaible" is left at the bottom left.
Clicking on the button will add the new messages to the current list (actually a refresh command will be issued, which should have the same effect except if you're in a multi-user environment and another user has already changed the messages so that they no longer match the "new" or "current" criteria).