Email Services

Question 1

Name 4 popular Linux MTA email packages?

Answer 1

postfix, send mail, exim, email

Question 2

Name 3 Linux MDA mail packages used for local email delivery and filtering

Answer 2

Procmail, sieve, binmail

Question 3

Name the 3 agent functions of a mail server

Answer 3

MTA, MDA, MUA

Question 4

What does MTA stand for and what does it do?

Answer 4

Message Transfer Agent, handles incoming and outgoing email

Question 5

What does MDA stand for and what does it do?

Answer 5

Message Delivery Agent, it handles the local delivery step. Common local delivery agents include procmail, binmail and sieve. Mail delivery agents commonly also handle mail filtering and automatic message replying.

Question 6

What does MUA stand for?

Answer 6

Message User Agent

Question 7

What does SMTP stand for?

Answer 7

Simple Mail Transfer Protocol

Question 8

What are the 3 types of user mailboxes commonly used on linux?

Answer 8

The mbox method (the /var/spool/mail file)
$HOME/mail files
Maildir mailbox directories

Question 9

Name 3 common MUA’s on Linux

Answer 9

binmail, Evolution, thunderbird

Question 10

What does POP stand for?

Answer 10

Post Office Protocol

Question 11

What does IMAP stand for?

Answer 11

Internet Message Access Protocol

Question 12

Name some basic SMTP Commands

Answer 12

HELO - opening greeting
MAIL - identify message sender
RCPT - identify message recipients
DATA - start of message
SEND - sends message to terminal
SOML - send or mail
SAML - send and mail
RSET - reset connection
VRFY - Verify username on system
EXPN - query for lists and aliases
HELP - Request list of commands
NOOP - No operation, does nothing
QUIT - Stop SMTP session
TURN - Reverses the SMTP roles

Question 13

Describe how you would manually send a basic SMTP message

Answer 13

telnet to mail host on port 25. Issue commands: HELO, MAIL FROM, MAIL TO, DATA, QUIT

For example:
telnet mail.mymailhost.com 25
HELO localhost
MAIL FROM: ted@localhost
RCPT TO: frank
DATA
This is a tests message
.
QUIT

Question 14

SMTP response codes are 3 digit codes in reply to command. The first digits denote the category of the response, these can be 50x, 21x, 22x, 25x, 45x, 55x. What categories of response codes are each of these?

Answer 14

50x Error
21x Information
22x Service
25x Action
45x Action
55x Action

Question 15

What is ESMTP?

Answer 15

Extended SMTP it adds extra commands and features to SMTP, ESMTP sessions are initiated with EHLO instead of the HELO greeting.

Question 16

What are the 3 types of authentiction used the the POP protocol?

Answer 16

USER/PASS - plain text (bad idea nowadays)
APOP - username in plain text, MD5 hashed password
AUTH - negotiates secure auth between client and server

Question 17

Name some POP3 client commands

Answer 17

STAT - mailbox status
LIST - list messages
RETR - return a specific message
DELE - delete a message
UIDL - provides UID for each message
TOP - lists most recent mesages
NOOP - no operation, does nothing
RSET - Resets the session
QUIT - terminates the session

Question 18

What are the two authentication methods available in IMAP?

Answer 18

LOGIN - Allows the client to use plain text usernames and passwords.

AUTHENTICATE - the client and server negotiate a common encrypted method.

Question 19

Name some of the IMAP Client Commands

Answer 19

There are many, not expected to remember all…
APPEND - Append a message
CAPABILITY - list imap servers capabilities
CHECK - create a checkpoint
CLOSE - Close the mailbox
COPY - copy a message between mailboxes
CREATE - creates a new mailbox
DELETE - Deletes a mailbox
EXAMINE - open mailbox in read-only
EXPUNGE - delete messages flagged for deletion
FETCH - Retrieve specified message
LIST - Lists all mailboxes
LOGOUT - Logout from the IMAP server
LSUB - list active mailboxes
NOOP - No operation, does nothing
RENAME - renames a mailbox
SEARCH - search messages for a string
SELECT - select a mailbox
STATUS - returns mailbox status
STORE - alter information associated with a message
SUBSCRIBE - adds mailbox to the list of active mailboxes
UID - set message references to UID (instead of seq. no)
UNSUBSCRIBE - removes mailbox from the list of active mailboxes