Are you saying that both the Public and Private keys will be sent in an email?

Yes, but only the public/private keypair of a temporary bitcoin address that your client loads with the amount of bitcoins you want to send to the person. Once you send it, your client should forget about it and not move additional coins into it.
The private key transactions would allow you to send bitcoins as text: through facebook, message board private messages, snail mail, basically any medium of communication. Bitcoinmail.com is not similar to this idea.