The 'Microsoft Apps' suite, i.e. Office Mobile, Lync 2010, PowerPoint Broadcast and OneNote, has been gradually being adapted for various Symbian smartphones with unusual requirements. In this case, it's the Nokia E6, with its higher resolution (though physically smaller) VGA display, which gets v2.1.5405 of the suite. This follows the N8 (with its smaller system [C:] disk) getting the update a week or so ago. Screenshot proof below.
As shown above, around 50MB is needed on your E6's system (C:) disk. Note that the Microsoft Suite is strictly optional, but does add a few refinements, including UI tweaks, to the built-in Nokia Email client. The existing Quickoffice software on your E6 shouldn't be affected, though the default handler for emailed Office documents will now be the Microsoft application.
This was spotted via Nokia Suite but it seems is also available via SW_update on the device, over the air.