Choose a VIP.
Only messages from the VIP are shown in the message list. If you can’t see expected messages, choose View > Sort By, then choose All Mailboxes (a tick shows it’s on).
When you’ve finished, click Inbox in the Mail sidebar or the Favourites bar to see other messages again.
You can also .
The person’s VIP mailbox is removed from the Use favourite mailboxes in Mail on Mac