Breath with me now: Ahhhhh...
I was an Outlook tester during the 2000 release; when the icon was first released internally, we were harshly critical of it in a very public way - it sucks to be the product that gets 'yellow' as your family color because it just doesn't work well at smaller sizes. We were very envious (you might even say 'green') of Excel, and hopping mad (say 'red hot'?) at powerpoint that they got nice icons and we got baby poop.
I heard later on that the designer ended up quitting shortly thereafter (not sure if it's true, never knew her name) and always wondered if our vitriol played a role.