My experience has been that PGP costs bucks ($$$) and GPG is free but a little buggy and not exactly end-user friendly. (kinda 'you get what you pay for' thing).

However if you go the GPG route, it does integrate with Eudora which is also free.

You'll definitely need to do some reading on the subject.

There are some good tutorials available too.

Also check out this post:

http://www.gossamer-threads.com/perl/gforum/gforum.cgi?post=261788