If CAcert provided you with a certificate, and if you wish you could include your actual name in it, I can grant you 15 out of the required 50 points, provided you actually show me two identification documents, at least one with a photography that looks like yourself. Ence we have to meet in real life.

You need a certificate to signe and/or cipher your mail:
  1. prove your are the sender of the message and that it has not been altered. But the head is offlimits so the subject of an e-mail is not protected !!!
  2. allow anybody (who has a certificate) to send you a secret message. Those messages are sent and stored encrypted on your computer, you have to provide the password of your certifiacte to read them. Messages are also encrypted on the computer of the sender, hence the certificate he needs.
As long as you certificate is anonymous, it does not assume your identity, but only that your e-mail address is not spooffed.