Looks like Microsoft has not forgotten about all the Windows Mobile 6.x users out there, pushing out a significant update to Mobile Outlook for some 6.x devices. It's unclear which devices are getting it exactly, but in this case here it's an HTC HD2 running Windows Mobile 6.5.5 23145.
Mobile Outlook was bumped to 18.104.22.16840 and is reportedly much more finger friendly, doing away with the annoying "tap to scroll right" notification. Overall, the update looks quite sharp and we're almost longing for our old Windows Mobile. Almost.
Big thanks to Rhys B., for the info and screenshots!