Using New Outlook on Windows for personal email, calendar, and contact management
I also rely heavily on the Search all mailboxes function. I think this is an essential function and needs to be included.
A related issue - when composing a message in the previous Outlook, there was the option to change the account from which it is sent, even after you had composed the email - in the New Outlook, changing the account deletes any content I have written - I may as well just create a new email. Managing multiple mailboxes is a constant challenge and this is another function being removed in the New Outlook.