wk2 email

Question 1

Sending email is dictated by what?

Answer 1

SMTP transaction

Question 2

Receiving email is covered by what?

Answer 2

either POP3 or IMAP

Question 3

What is SMTP

Answer 3

Simple Mail Transfer Protocal - a communication protocal for receiing or sending mail. User-level email clients typically use SMTP only for sending messages to a mail server for relaying

Question 4

What is POP3

Answer 4

Post Office Protocol version 3 - an application-layer protocal used by email clients to retriieve email from a mail server

Question 5

How does sending email work on a cpanel server in a nutshell?

Answer 5

• Customer/client types up an email and hits send
• Exim is listening for the connection and has a transaction with the customer/client
• Exim checks the MX record for the domain after the @ in the TO field of the email

Question 6

What are the stock SMTP ports

Answer 6

SMTP :25
SMTPS :465

Alternate SMTP :26
Alternate SMTPS :587

Question 7

How receiving email with POP works in a nutshell?

Answer 7

mail client (mac mail, thunderbird, outlook, etc) sends request to the mail server (which may be the same as their SMTP server)

Question 8

What are the stock POP Ports?

Answer 8

POP :110

Secure POP :995

Question 9

How receiving email with IMAP works in a nutshell?

Answer 9

mail client app (outlook, etc) sends request to mail server (might be same as their smtp server) using the IMAP listening port

the app listening on the IMAP port, dovecot in the case of cPanel, accepts the connection and then has a conversation with the client

With IMAP, there can be a more comlex converstaion occuring back and forth between client and server than what you might see in POP or SMTP.

Ultimately IMAP takes a number of tasks that were client-side and makes them server-side.

Question 10

Stock IMAP ports

Answer 10

IMAP :143

Secure IMAP :993

Question 11

In order of preference/usefulness, how do you check what exim is currently processing?

Answer 11

exiwhat
shows active connections being handled

ps -C exim wwwu
shows a list of all running exim processes.

lsof -c exim
shows a list of files being accessed by exim

Question 12

Where are the exim logs?

Answer 12

/var/log/exim*

exim_mainlog
exim_rejectlog
exim_paniclog

/var/log/exim_mainlog
    Logs message arrival and delivery attempts
    The output is controlled by the log_selector option
/var/log/exim_rejectlog
    Logs delivery rejections based on policy (e.g. ACL)
/var/log/exim_paniclog
    Logs server errors, such as those that cause exim to crash, or those that cause a message to never be delivered.
    Should be empty, or nearly empty.

exim -bP log_file_path will display the log file path.

Question 13

Attempts to send the message that matches the input ID.

Answer 13

exim -M

Question 14

This will process the entire exim queue again. Adding an additional f (-qff) will force frozen messages as well.

Answer 14

exim -qf

Question 15

This is using the mail command, but it runs the debugger, so that you can see any snags along the way.

Answer 15

exim -odf

Question 16

This will print the total count of queue messages. This number should be low. If it’s high, it needs to be investigated.

Answer 16

exim -bpc

Question 17

This summarizes the queue for you

Answer 17

exiqsumm

Question 18

This extracts statistics from the log

Answer 18

eximstats

Question 19

This will check acceptance from a given IP address to the mail server

Answer 19

exim_checkaccess

Question 20

Where’s the exim config file? (you shouldn’t manually edit it)

Answer 20

/etc/exim.conf

Question 21

What is dovecot

Answer 21

Dovecot is an open-source IMAP and POP3 email server, written with security primarily in mind. It is a fast and simple setup that requires no special administration and uses very little memory.

As we mentioned earlier in How Email Works, Dovecot is the default POP/IMAP application on a cPanel server. The system uses /etc/dovecot/dovecot.conf to initialize the Dovecot service with settings the end-user defines. This can also be configured in WHM’s Mailserver Configuration interface.

Question 22

What’s the name of doveccot’s administration tool?

Answer 22

doveadm

Question 23

Locate, test, or reopen Dovecot’s log files

Answer 23

doveadm log

Question 24

This will show who is currently logged into the dovecot server

Answer 24

doveadm who

Question 25

Tests authentication for a user

Answer 25

doveadm auth

Question 26

This will fetch messages matchin a given search query

Answer 26

doveadm fetch

Question 27

Shows a list of mailbox GUIDs and message UIDs matching a given search query

Answer 27

doveadm search

Question 28

This will inspect or reset stats

Answer 28

doveadm stats