According to this [link|http://support.microsoft.com/default.aspx?scid=kb;en-us;Q266418|KB Q266418], Outlook 2K+ installs a stub mapi32.dll in win\\system32 which routes calls to the "real" mapi32.dll further down the directory tree. Exchange overwrote that stub with a real mapi32.dll file. Nifty...

It may be just me, but perhaps "Gordian" would be a good replacement for "XP" in next year's version of things...