When the network layer receive the e-mail message, the intermediate machine checks to see if it is the correct destination, which it is NOT. So it will send the e-mail message back to layer 2 (Data Link Layer).
When the network layer receive the e-mail message, the intermediate machine checks to see if it is the correct destination, which it is NOT. So it will send the e-mail message back to layer 2 (Data Link Layer).