If you are using more than mailaccount it is simply painful to tipp you up and down the different mailaccounts. One top view for all unread mails.
i have more than 20 mailaccounts. so it is toilsome always tipp on an account, incoming mail, then tipp on the mail, read them, an go all the way back.
This is an interessting thing if you have one mailaccount, but not for the understanding off a bussines-phone.