Khóa học Mail Administration in WHM
Introduction
Welcome to Managing Mail in WHM. We're going to review some information about how internet mail works and then discuss some of
the options in WHM. The modules discuss setup, configuration, and message and notification management through WHM. You will also
learn how to understand messages from the mailer daemon, review mail related statistics and troubleshoot common mail problems
While we are covering a lot of material there are features and options that we do not discuss. Our hope is that by the time
you complete the course, you will be comfortable enough with mail management through WHM to engage in further study independently
We encourage you to use a test server to explore the areas we can not cover in detail here.
POP3, IMAP, STMP
Exim and SMTP
STMP (Simple Mail Transfer Protocol) is the protocol used to send mail. It is spoken by Exim on cPanel servers. Exim
takes mail from user's mail clients and delivers it either to local mailboxes or remote mail server (using SMTP). Local
mail delivery can be complicated and includes executing forwards and filters. Exim also checks to see if mail should
be scanned by Spam Assassin and if so, facilitates that process.
Devecot, POP3 and IMAP
Mail is retrieved from local mailboxes using either POP3 or IMAP protocols. These protocols are spoken by Devecot
on modern cPanel servers
2. Set Up Mail
Unit Objectives
Understand the major features of Devecot
Demonstrate how to change the configuration options for Devecot
Understand why it's important to set up the mail system preferences
Demonstrate how to set up the mail system preferences
Introduction
WHM Home -> Service Configuration -> Mailserver Selection
Devecot is the default and recommended mail server.
In 11.54 and later, it is the only mail server option.
Courier: Traditional cPanel IMAP and POP3 server; Extremly reliable.
Devecot: Low memory footprint; Highly configurable; Excellent security track record
Better IMAP performance; BlackBerry Fastmail support
WHM Home -> Server Contacts-> Edit System Mail Preferences
We will practice mail forwarder setup for system accounts. This prevents important notifications
from becoming frozen in the queue.
Authentication
To verify that someone is who they claim to be. In the computing world, this is frequently done with a password
Forwarder
In email, to automactically send mail that was sent to one address, to another address
Server load
How much work the server is doing at a given moment. Usually displayed in 1, 5 and 15 minute averages
Old Mail Server Sofware
Previous to 11.54, there was a mail server called Courier in use on some servers. During the upgrades to 11.54
everyone still using Courier is automatically migrated to Devecot
There is also an even older mail server call cppop. This mail server has been depreciated for years and we strongly
encourage everyone to migrate to Devecot
This course only covers the Devecot mail server software. Additionally, it does not cover very Devecot feature. Full
documentation can be found at http://go.cpanel.net/configure_dovecot
An authentication daemon is a program that logs the user in and does the work to ensure that the correct password is
being used. Devecot provides authentication services for email on a cPanel server. A user cannot receive mail until
after dovecot's authentication daemon is done checking the password. Unless POP-before STMP services are turned on in
Tweak Settings, user cannot send mail off the server until after their password has been checked
Dovecot spawns and kills authentication daemon(processes) based on the volume of requests. If your server tends to have
user send or check their mail in large but quick bursts the authentication daemon settings may need to ben adjusted
to reach the optional balance between availability of services and server load
This is controlled in WHM -> Service Configuration -> Mailserver Configuration
Mailserver Configuration - Emptying Trash
Dovecot does not empty trash by default
In order to enable automatic trash disposal, you need to select the "Auto Expunge Trash" option in WHM -> Service
Configuration -> Mailserver Configuration
Dovecot Warnings: Time moved backwards
The most commnon waring seen for the Dovecot is the "time moved backward" warning.
This is not an error with the mail server. It is a warning that there is a problem with the time on the server detected
by the mail server software. The issue occurs mostly on virtual machines. The most common way to resolve the issue is to set up
ntp to keep the server's time steady.
Edit System Mail Preferences
There are three system accounts that do not receive mail: root, cpanel and nobody. These accounts need to have forwarders set
up for them in Edit System Mail Preferences. If the mail is not forwarderded, then the mail will freeze in the queue
WHM Home -> Server Contacts -> Edit System Mail Preferences
Mailbox Formats
In version 58, cPanel added a new mailbox format:mdbox. This format was added to reduced inode usage and disk i/o,
improve performance and allow for faster backups and restores. We will discuss the details of MailDir and mdbox in
the Administering Mail from the Command Line course
You can switch between the two formats per cPanel user using the wizard in WHM at Home -> Email -> Mailbox Conversion
Review
Dovecot is the POP3 and IMAP mailserver
Dovecot has many configuration options, described in the interface and the documentation
Mailserver may need to have their maximum number of total and idle authentication processes configured to avoid
both wasting resources and receiving errors
System mail accounts need to be forwarded to avoid having mail freeze in the queue
The new mailbox type mdbox features reduced inode usage, reduced disk i/o, improved performance, and faster backups and restores
3. Exim and spamd Configuration
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