We've been seeing updates to Outlook Mail and Calendar at least weekly, but at least there's now a major new feature - the ability to 'link' inboxes and thus show email from multiple accounts at the same time. It works, but it's... a little glitchy, as I show below. 

This update adds the ability to link any or all of your Outlook inboxes into a single, unified inbox:

'Manage accounts' is on the '...' menu, offering a 'Link inboxes' function...

Just tick the ones you want linked and then wait.... in my case it took 10 minutes and almost 2000 emails before the syncing stopped and Outlook let me back into my emails. Data points welcome if it's any smoother (or worse) for you!

You can update Outlook Mail and Calendar in the Store in the usual way, of course. It's a complicated application in many ways and I'm sure it'll get lots more tweaks before the end of 2015.