CentOS Mail Linux Server

In this chapter we are going to discuss about

Basic Postfix Mail server setup on CentOS Linux

• Installing Postfix Mail Server on CentOS Linux

• Changing Default CentOS Linux Mail System (MTA)

• Postfix Configuration (SMTP)

• Test your Postfix SMTP Connection

• Mail Aliases

• POP/IMAP Setting (Configuring Dovecot)

• Mail Security Checklist

Step by Step Guide on Postfix Mail Server with Virtual Users and Multiple Domains

• Step1:  Install Postfix with Mysql Support and remove Sendmail

• Step2: Create Virtual User, Configure Postfix, Dovecot and Mysql

• Step3:  PostfixAdmin Installation

• Step4:  Squirrelmail Installation

• Step5: Create virtual Users and multiple  virtual domain using PostfixAdmin

• Step6: Verification on PostfixAdmin settings and SMTP, POP3 test

• Step7: Enhance Postfix Mail Server Security by implementing SMTP Authentication using Dovecot SASL

• Step8: Fine tuning Postfix mail queue

• Step9: Fetching email from other mail server

QMail Mail server on CentOS Linux with Virtual Users and Multple Domains

• Step1: Install Qmail Mail Server on CentOS Linux

iRedMail Mail server on CentOS Linux

• Upgrade iRedAdmin-Pro-1.1.0 from iRedAdmin Free Edition

• Customization 1: Solving Recipient Address - Rejected Domain not Found Issue

• Customization 2: Disable Greylisting and Blacklist

• Customization 3: Isolate iRedAdmin, PhpMyAdmin, PHPLDAPAdmin and Roundcubemail

A complete email system is build up 3 main components:

MUA (Mail User Agent)

MUA resides at client side, this is normally refer to client email application such as MS Outlook, Out Express, Thunderbird, SeaMonkey, putt, pine etc.  MUA is responsible for sending and receiving email to/from MTA.

MTA (Mail Transport Agent)

MTA is responsible for accepting, receiving and delivering task within hosts/ servers an. Few well-known MTA application you might already known is MS Exchange Server, Sendmail, Postfix and Qmail.

MDA (Mail Transport Agent)

MDA is responsible for delivery emails from MTA then redirect them according to user's mailbox.

A mail server is using the following TCP protocols:-

Simple Mail Transfer Protocols (SMTP)

The default SMTP port is 25. However, you might customize the port (for example port 587), this is due to some ISP blocking smtp port number 25 for dynamic IP. SMTP is used as communication port within MUA to/from MTA and MTA to/fromm MTA. Generally, user sending email is using SMTP port

Post Office Protocol (POP)

The default POP port is 110 .POP is used for receiving/download email from mail server. When POP is running, it will retrieve user's  email from  the mail server, delivery it to user local machine/pc then remove it from server.

Internet Message Protocol (IMAP)

The default POP port is 110. IMAP is another famous protocol used for retrieving email from mail server. Unlike POP, IMAP will first download the subject header from mail server, when user click on the subject, email content will be downloaded to user's local machine, while still kept a copy of email from the server

CentOS Email Options

There are more than 3 different email servers option in CentOS. The famous email server packages are:

• Sendmail

• Postfix

• Qmail

I been working on Sendmail and Postfix for few year. Personally, I found Sendmail is  a flexible and powerful but you need to take extra careful for your configuration.

Postfix on the other hand are less flexible but it has take care of most of the security concern.  We will start our sharing session here with my favorite email program Postfix

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