It wasn't obvious for me either. I also didn't get the scrolling element. It seems to be a merge of emails and todo? Still not really clear. Perhaps an introduction video could help? I'm also concerned on information security. There could be a really clever solution how full privacy and match prioritising emails. Senders and subject lines are sensitive.
At work I currently get 1000-2000 email per day, of which about 500 need personal attention, including calendar invites. This sounds horrendous, and it ain't great, but Outlook is surprisingly adept at rule setting, being really responsive, and integrated with Office (and to a lesser extent Skype, OC was more pleasurable for the from a UX perspective) to make this manageable.
