Postfix Mail System - Step by Step Guide

Part 1:  Install Postfix with Mysql Support and remove Sendmail

Installing of Postfix, Postfixadmin, Dovecot and Squirrelmail is not an easy task. There are some customization works you need to be done in order to get it works. I hope the following guide step by step instruction will be handy for you :)

My mail server system information:

hostname : example.centos.local

IP address: 192.168.139.128

Netmask   : 255.255.255.0

Gateway  : 192.168.139.2

There are 2 domains that I will setup for this guide. There are

domain name : abc.local

user mailbox  : alex@abc.local

domain name : xyz.local

user mailbox  : yasmin@xyz.local

The postfix admin login we will be using is post@example.local, where example.local will not be created in Postfixadmin's virtual domain. This is to show you that, the email system we setup later is solely running on Postfixadmin's virtual domain

Note:

• I am going to show you only setup a mail server that works within your local Lan. To sent a mail outside your organization, you must make sure you have a valid domain name, DNS and MX record is configure properly. You need to change the host file under /etc/hosts  and check the /etc/nsswitch.conf to speed up the dns resolve.

• My system is current SELinux disabled. If you wish turn Postadmin on, please relocate your Postfixadmin into /usr/share

Step 0: Install prerequisite packages

If you cannot install the packages in one line, then try to install them one by one.

Step1: Backup the current Sendmail configuration

CentOS Linux default MTA is Sendmail. Since we are swtching to new MTA-Postfix. It is advisable to backup current sendmail config and bin to new location before we proceed.

First, I will create new folder call backup. Next, I backup all the files and record the sendmail path to a text.

 

#mkdir /backup #touch /backup/sendmail.config.location.txt #which sendmail mailq newaliases > /backup/sendmail.config.location.txt   #which sendmail mailq newaliases /usr/sbin/sendmail /usr/bin/mailq /usr/bin/newaliases #cp -var /usr/sbin/sendmail /backup #cp -var /usr/bin/mailq /backup #cp -var /usr/bin/newaliases /backup

Step2  Add in CentosPlus repos for postfix

Postfix installation by CentOS default repo does not support mysql addon. We need to use the specified postfix that enable the mysql support. Also, we want to avoid any disruptive update on our customised postfix package, you need to add in  exclude=postfix-* for base and updates repo.
 

 

#vim /etc/yum.repos.d/CentOS-Base.repo   #additional packages that extend functionality of existing packages [centosplus] name=CentOS-$releasever - Plus mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus #baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/ gpgcheck=1 enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5[base] includepkgs=postfix-* [base] name=CentOS-$releasever - Base mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os #baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/ gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 exclude=postfix-* #released updates [updates] name=CentOS-$releasever - Updates mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates #baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/ gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 exclude=postfix-*

Step5: Install postfix from centosplus repo

The default package of posftfix does not work with Virtual Domains and Virtual Users.  If you have installed it earlier, you must remove it. Use "rpm -e" or "yum remove"  to remove it.

If you are not install postfix yet, the run the following command will only download and install te postfix from centosplus.

Step6: verify the postfix package installed

Now, let us check the packages information been installed. Good, that is the package that we need.

Step7: verify the postfix package support the mysql

Before proceeding with the Postfix configuration, make sure that the postfix version you have has MySQL support. run postconf -m and verify that mysql appears in the list. If mysql isn’t there, uninstall postfix using yum. Then, download the centosplus repository again, and install manually.

Step8 : Install system-switch-mail, mysql, system-switch-mail,dovecot, squirrelmail

Now, let us download all the packages we need.

#yum -y install  php-mysql php-imap, php-ldap,  php-mbstring

Step9: Switching default Sendmail to Postfix Linux mail system

The system-switch-mail tool is the Mail Transpot Agent Switcher that enable you to switch within various Mail Trainsport Agent that installed at your system. If your system is using Sendmail by default, we need switch to postfix.

 

#system-switch-mail

Step10: verify the setting of our new MTA

Before we proceed further configuration, lets us verify on the default MTA setting. If everything is correct, you should see the highlighted text changed to sendmail.postfix

#alternatives --display mta mta - status is manual. link currently points to /usr/sbin/sendmail.postfix

We also going to check if our mailq, sendmail and aliases has the correct configured with postfix

#ls -l  /etc/alternatives/mta-*   lrwxrwxrwx 1 root root 40 Mar 13 14:08 /etc/alternatives/mta-aliasesman -> /usr/share/man/man5/aliases.postfix.5.gz lrwxrwxrwx 1 root root 22 Mar 13 14:08 /etc/alternatives/mta-mailq -> /usr/bin/mailq.postfix lrwxrwxrwx 1 root root 38 Mar 13 14:08 /etc/alternatives/mta-mailqman -> /usr/share/man/man1/mailq.postfix.1.gz lrwxrwxrwx 1 root root 27 Mar 13 14:08 /etc/alternatives/mta-newaliases -> /usr/bin/newaliases.postfix lrwxrwxrwx 1 root root 43 Mar 13 14:08 /etc/alternatives/mta-newaliasesman -> /usr/share/man/man1/newaliases.postfix.1.gz lrwxrwxrwx 1 root root 23 Mar 13 14:08 /etc/alternatives/mta-pam -> /etc/pam.d/smtp.postfix lrwxrwxrwx 1 root root 22 Mar 13 14:08 /etc/alternatives/mta-rmail -> /usr/bin/rmail.postfix lrwxrwxrwx 1 root root 25 Mar 13 14:08 /etc/alternatives/mta-sendmail -> /usr/lib/sendmail.postfix lrwxrwxrwx 1 root root 41 Mar 13 14:08 /etc/alternatives/mta-sendmailman -> /usr/share/man/man1/sendmail.postfix.1.gz

Step10: Remove Sendmail packages

My previous post suggest that although both mail server packages (Sendmail and Postfix) are compatible with each other. I strongly suggest you remove Sendmail packages to only allow one mail system in the sever. Due to CentOS Linux needs minimum one mail server installed. You must make sure that you installed Postfix first then remove Sendmail! Else, you will faced with some libraries dependencies issues.

To remove Sendmail packages, please use rpm -e command

Back to Step by Step Guide on CentOS Linux Postfix Mail Server

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