Send Email With Different Return Address

Using the linux mail or mailx commands you can send email with a return address other than your own. If you type something like this "mail cowman@cheese.com -r cowman@cheese.com" it actually looks like the recipient got the email from them selfs. This is pretty cool. The only thing is if the computer knows the address it doesn't automatically say the same of the person, but displays the email address as the from, so somehow I think the computer can still differentiate.