http://www.codeproject.com/dll/plugin.asp?df=100&forumid=4163&exp=0&select=567833
http://www.codeproject.com/atl/Outlook_Addin_Tutorial_-1.asp
http://blogs.msdn.com/dancre/archive/2004/03/21/93712.aspx
Calendaring survey:
http://slashdot.org/askslashdot/00/11/24/2255239.shtml
LDAP and pkcs:
http://www.google.com/search?hl=en&lr=&q=ldap+public+key+lookup