Postfix is fast and popular SMTP server widely used. The main job of postfix is to relay mail locally or to intended destination outside the network. Some of the most popular SMTP servers are Sendmail, Postfix and Qmail. By default Sendmail comes pre-installed with CentOS/RHEL 5. We will need to remove it and install Postfix.
Step 1: Install Postfix
If Postfix not already installed on your machine, Install it using following command. Also remove sendmail if already installed.
# yum remove sendmail # yum install postfix
Make postfix as default MTA for your system using following command
# alternatives --set mta /usr/sbin/postfix
If above command not work and you get output as “
# alternatives --set mta /usr/sbin/sendmail.postfix
Step 2: Configure Postfix
Let’s start postfix configuration. Edit Postfix configuration file /etc/postfix/main.cf in your favorite editor and make following changes.
myhostname = mail.tecadmin.net mydomain = tecadmin.net myorigin = $mydomain inet_interfaces = all mydestination = $myhostname, localhost, $mydomain mynetworks = 127.0.0.0/8, /32 relay_domains = $mydestination home_mailbox = Maildir/
After executing above command edit postfix configuration file and make sure all changes done properly.
Step 3: Restart Postfix Service
As we have done basic Postfix configuration, So restart Postfix service to read changes of configuration. Also configure to auto start on system boot.
# service postfix restart # chkconfig postfix on
Step 4: Open Firewall Port
Now if your system is configured to use iptables firewall, So add firewall rules to make postfix accessible from outside, using following commands.
# iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 25 -j ACCEPT # iptables -A INPUT -m state --state NEW -m udp -p udp --dport 25 -j ACCEPT
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