viewing all Mailbox inbox contents simultaneously.

After upgrading to Big Sur I have this frustrating thing happened in Mail where in the left hand column in Mail I have my three accounts listed separately and to view new mail I have to highlight each one individually to see mail in that account. I used to be able to see all new mail in all accounts simultaneously. I have tried everything but cant find a way of implementing that. At the top of that left hand column I have 'favourites' and below that 'smart mailboxes' and below that the individual accounts listed. Help its annoying!