On Tuesday, I wrote about some of the new features in Outlook 12 and, in passing, I mentioned that Outlook was the single biggest consumer of the Ribbon.

Not surprisingly, since I didn't explain the remark any further and because it seems to contradict my post about what apps get the new Office UI, I got a lot of feedback questioning my remark.  "Surely you're mistaken... or crazy?" one reader wrote in.

While it is true that I have been quite sick this week and woke up with a > 100 degree fever again yesterday morning, I assure you that I am not, in fact, any crazier than usual.

(That's 37.8 C for you non-United Statesians...)

Anyway, while it is true that part of Outlook has the new UI and part of it does not, the half which does required the design of more Ribbon tabs than the rest of Office combined.

Start with the fact that in Office 12, the Outlook editing and reading canvas is based on Word.  This means that the feature set of an e-mail message starts with "everything you can do in Word", subtracts "things that don't make sense in an e-mail, such as page orientation" and adds "all of the features Outlook supports."

And now, you've successfully designed the Ribbon for one scenario: sending an e-mail message.

However, there are so many different scenarios within Outlook: post a message, send a meeting request, accept a meeting request, counter-propose a meeting request, accept a task, resend a message, read a non-delivery receipt, forward an iCalendar, etc.  In fact, there are more than 40 unique "application experiences" within Outlook, each which requires a set of tabs in the Ribbon that 1) expresses all of the possible functionality  2) is as consistent as possible with other similar features within Outlook and  3) is as consistent as possible with the Word experience.

So, while it might seem like Outlook is just dabbling its toe into the new UI, in fact Outlook contains the largest and most complex set of scenarios to utilize the Office 12 UI.  As a result, Outlook is probably the place where we've done the most revisions of the Ribbon experience since Beta 1.  Of course, we've made improvements in every app based on feedback, but the Outlook tabs have really been overhauled to make them more straightforward to use.

Which is good, because Outlook is the place people do most of their reading, writing, and document creation.