Application Layer (7) Protocol Commands

Question 1

These commands are used to identify the SMTP client to the SMTP server.

Answer 1

SMTP Extended HELLO (EHLO) or HELLO (HELO)

Question 2

This command is used to initiate a mail transaction in which the mail data is delivered to an SMTP server that may, in turn, deliver it to one or more mailboxes or pass it on to another system.

Answer 2

SMTP MAIL (MAIL)

Question 3

This command is used to identify an individual recipient of the mail data; multiple recipients are specified by multiple uses of this command.

Answer 3

SMTP RECIPIENT (RCPT)

Question 4

This command causes the mail data to be appended to the mail data buffer.

Answer 4

SMTP DATA (DATA)

Question 5

This command specifies that the current mail transaction will be aborted.

Answer 5

SMTP RESET (RSET)

Question 6

This command asks the receiver to confirm that the argument identifies a user or mailbox.

Answer 6

SMTP VERIFY (VRFY)

Question 7

This command asks the receiver to confirm that the argument identifies a mailing list, and if so, to return the membership of that list.

Answer 7

SMTP EXPAND (EXPN)

Question 8

This command causes the server to send helpful information to the client.

Answer 8

SMTP HELP (HELP)

Question 9

This command does not affect any parameters or previously entered commands. It specifies no action other than that the receiver send a “250 OK” reply.

Answer 9

SMTP NOOP (NOOP)

Question 10

This command specifies that the receiver MUST send a “221 OK” reply, and then close the transmission channel.

Answer 10

SMTP QUIT (QUIT)

Question 11

OK; indicates that the request has succeeded

Answer 11

HTTP RESPONSE 200

Question 12

Bad Request; the server cannot or will not process the request due to something that is perceived to be a client error

Answer 12

HTTP RESPONSE 400

Question 13

Forbidden; the server understands the request but refuses to authorize it

Answer 13

HTTP RESPONSE 403

Question 14

Not Found; indicates that the server cannot find the requested resource

Answer 14

HTTP RESPONSE 404

Question 15

Internal Server Error; indicates that the server encountered an unexpected condition that prevented it from fulfilling the request

Answer 15

HTTP RESPONSE 500

Question 16

Bad Gateway; indicates that the server, while acting as a gateway or proxy, received an invalid response from the upstream server.

Answer 16

HTTP RESPONSE 502

Question 17

Gateway Timeout; indicates that the server, while acting as a gateway or proxy, did not get a response in time from the upstream server that it needed in order to complete the request

Answer 17

HTTP RESPONSE 504