Today I accidentally hit Shift+Insert in Windows XP Service Pack 3 with Outlook 2003. An email message form popped up with the latest clipboard entry already inserted into the body of the message. Is this common to all versions of Outlook?
Shift+Insert is actually a Windows command for Paste that dates from at least Windows 3.1. It is valid in just about any Windows application, but in the case of Outlook, you had text that Outlook knew how to enter in a message, so it assumed that's what you wanted to do.
FYI, similar commands to the Shift+Insert for Paste are: Ctrl+Insert for Copy and Shift+Delete for Cut.