Link to outlook: protocol in Views
The problem is that the URL code in Drupal doesn't recognise your "outlook:" prefix, and so is trying to make it a valid version of a protocol it does know. Option (2) explicitly invokes the URL code, so it is not surprising that it changes the href.

I am slightly surprised that the rewrite version didn't work, and can only assume you had other options set in the View which caused this -- or that the page was cached.

If you cannot get the rewrite to work, I suggest you override the field with a view-specific field template (see "theme information" in the theme config), in which you can do whatever you wish.