Mail Server Configuration in CentOS using Postfix

First thing to do is check if postfix and dovecot is installed in your Linux Machine
rpm -qa postfix
rpm -qa dovecot

If postfix and dovecot is not installed, then install it using yum command
yum install postfix dovecot -y

Now lets start configuring Mail Server:

1. Look for the below line and make necessary changes in vi /etc/postfix/main.cf

myhostname = mail.yj.bt
mydomain = yj.bt
myorigin = $mydomain
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mynetworks = 127.0.0.0/8, 10.0.0.0/24
home_mailbox = Maildir/
smtpd_banner = $myhostname ESMTP
# Add at bottom for
# for SMTP-Auth setting
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth-client
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
smtpd_client_restrictions = permit_mynetworks,reject_unknown_client,permit
smtpd_recipient_restrictions = permit_mynetworks,permit_auth_destination,permit_sasl_authenticated,reject

2. service sendmail stop
3. chkconfig sendmail off
4. Change the MTA from sendmail to Postfix

alternatives --config mta

5. service postfix start
6. chkconfig postfix on
7. Look for the below line and make necessary changes in vi /etc/dovecot.conf

protocols = imap imaps pop3 pop3s
mail_location = maildir:~/Maildir
mechanisms = plain login
socket listen { # uncomment
client { # uncomment
path = /var/spool/postfix/private/auth-client
mode = 0660 # uncomment
user = postfix # add new line
group = postfix # add new line
} # uncomment
} # uncomment

8. service dovecot start
9. chkconfig dovecot on

That's it, your linux machine will now function as mail server. Isn't that very simple for setting up a simple mail server. Please be mind that there is MX entry in your DNS point to the IP address of your mail server.