We all recall PGP the cool email encryption master of the 90’s, however after going commercial and tumbling a bit around the idea more or less died out, maybe because of the introduction of certificate based counterparts.
Never the less it was very cool and worked very well, and now for the good news, it has gone GNU and is awailable once again as free software, now I make it sound like this is breaking news – its not but I just recently stumbled upon it :-).
It also integrates into MS Office 2003/2007 nice
Check the website;
http://gpgee.excelcia.org/
Alternative
Just stumbled across yet another GNU open PGP util, have not tried it and it does not appear to have support for Office, but may still be worth a look;
Enigmail – http://enigmail.mozdev.org/home/index.php