There are many functions related to sorting mails but not so much in regards to sorting mailboxes.
I have several mailboxes and I recall when I worked for DaimlerChrysler we used Lotus Notes and could pin each different mailbox in Horisontal Tabs, below the main Pane. This was true even after we at Mercedes-Benz dumped Chrysler and until we dumped Notes as main mail software. However, that was not equal to choosing a better e-mail software, according to a vast majority of your employees back then, about 2008.
Now, I have spent quite some time looking for someone to add Tabs as a plugin or enhancement or extension to Outlook but have yet to see anyone doing this, not even Microsoft. So when will this be available again, because many with me are sick and tired of scrolling in the default left pane for meters and meters to handle mailboxes and folders. It is not productive, or efficient, or user friendly in any way.