The front page in the email app is a list of email accounts, click on each one and you only see the emails for that account. That's where you have your separation. They don't put all your eggs in one basket at all.

The unified unread mail inbox below the email accounts list is, at least for me, a nice way to triage all my unread mail although perhaps Jolla might want to let users select which accounts are shown in that list.

I'm sure we'll see changes when they do their tablet UI as tablet real-estate allows an almost traditional desktop layout.