You know you're doing well when your product is used not just on Earth, but in outer space as well. That's something Microsoft can boast with its Outlook email client, which was used on the space shuttle Atlantis , as well as the International Space Station.
Office Watch has a pretty interesting write-up on the whole ordeal, describing how the astronauts use Outlook 2003. It's a little different than what you might think. According to Office Watch, the crew is equipped with fairly standard laptops running Outlook 2003 with Exchange Server, only they don't link to the server using any of the standard methods.
All incoming and outgoing messages are bundled into a tidy file and exchanged one-by-by through a network link. This happens just a few times a day, when NASA uploads a small .OST file to each crew member. Unlike a regular .OST file, this one is nothing more than a container for exchanging groups of messages - no calendar, contacts, or anything else typically found in one.
There isn't a whole lot of bandwidth to work with, so extra effort is made to keep the .OST file as small as possible, usually no more than 4MB, as least for the space shuttle. OST files bound for the ISS typically check in at 30-40MB.