(10 points) Look at the picture below describing the sending and receiving of emails. Answer the questions below. 4. sender receiver sender's mail server receiver's mail server a. b. c. In step 1 above, what is the protocol used to send email from sender's user agent to sender's email server? In step 2 above, what is the protocol used to send email from user's email server to receiver's email server? In step 3 above, what is the protocol used by receiver's user agent to receive email from receiver's email server? You can name more than one. In step 2 above, if the receiver's email server is down, can the sender's email server send the email to a third party who can store the email temporarily for the receiver's email server? In step 2 above, what will the sender's email server do, if the receiver's email server is temporarily down? d. e