Editing Emails?

Hello Everyone,

New in here, hope to learn some new wealth and knowledge about computers.I have a question for all you computer persons who are familar with emails. Please advise if this subject has been covered already and i'll try to read some history files on here....

Say I send an email (via hotmail) to a friend Bob. It reads, 'Bob you are a great person and a good friend!'

Could Bob interfere with this email and state or re write something that wasn't originally sent?

I believe there is 'authentication' and r'outing information' stored with all emails?????

Could some one explain how simple or complex this is to do, or if this is possible at all?

Thanks in advance

 

I think you might want to look into pgp for securing such things.
http://www.pgp.com/downloads/desktoptrial.html