Now the Ethernet packet finally travels over the wire to the destination, which snarfs it up and tries to decode it. The receiving computer's operating system spies that IP is being used so it sends the packet "up" through the IP layer, which decodes it and sends it "up" through the TCP layer, which further sends the constantly shrinking packet up to SMTP, which then delivers it to the receiving human who is reading her mail, unaware of the intricate complexity underneath the seemingly simple communication.