How to setup postfix + dovecot mail server based on CentOS 6.2

This have been taking me hours to configure it.

1. Stop the sendmail service and remove it

> service sendmail stop
> yum remove sendmail

2. Install Postfix and Dovecot

> yum install postfix dovecot

3. Edit you hosts file and Add 'mail.yourdomain.com' and 'mail' to 127.0.0.1

> vi /etc/hosts

4. Edit the programs configuration. Mostly about user, servername, etc...
(Will edit later for details)

> vi /etc/postfix/main.cf
> vi /etc/dovecot/dovecot.conf
> vi /etc/aliases

4A. postfix/main.cf sample, configs that added.

myhostname = mail.yourdomain.com
mydomain = yourdomain.com
myorigin = $mydomain
inet_interfaces = all 

inet_protocols = ipv4 # required for CentOS 7 ~ 

#mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mydestination = $myhostname, $mydomain
mynetworks = 192.168.0.0/24, 127.0.0.0/8
#relay_domains =
home_mailbox = Maildir/
smtpd_recipient_restrictions=permit_mynetworks,reject_unauth_destination
#relayhost = your-hosting-site-mail-relay.yourhostingsite.com

FIGURE 4B. dovecot.conf sample, configs that added.

protocols = imap pop3
mail_location = maildir:~/Maildir
pop3_uidl_format = %08Xu%08Xv 

FIGURE 4C. /etc/aliases sample

# Person who should get root's mail
root:           kiddokenshin

5. Switch your MTA configuration and make sure is SMTP

> alternatives --config mta

6. Add mail user account (without SSH login)

> useradd -s /sbin/nologin youruser
> passwd youruser
> echo "youruserpasswd" | saslpasswd2 -p -u yourdomain.com -c youruser
> sasldblistusers2
> chgrp postfix /etc/sasldb2

7. Start your mail server

> service dovecot start
> service postfix start

8. Check your smtp port availability

> telnet localhost 25

Remember to add MX record and CNAME record on your domain manager. Most probably your mail server is working right now.

!! CAUTION !!
- If you cant send your mail out, most probably its the firewall's fault.
- Some rental server(or hosting site) required you to relay to their mail server to send mail.

If you like to use web browser to view and reply mail,
follow the optional instruction below to install the web based mailer, squirrelmail.

Installing squirrelmail (Optional)
A. Install EPEL Repository

> wget http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
> rpm -i epel-release-6-5.noarch.rpm

B. Install and Config SquirrelMail
(configure your squirrelmail, such as server name, smtp domain etc...)

> yum install squirrelmail
> /usr/share/squirrelmail/config/conf.pl

C. Edit httpd.conf and Restart httpd (assuming you have httpd)

> vi /etc/httpd/conf/httpd.conf
> service httpd restart

SAMPLE of httpd.conf

Alias /squirrelmail /usr/share/squirrelmail
<Directory /usr/share/squirrelmail>
    Options Indexes FollowSymLinks
    RewriteEngine On
    AllowOverride All
    DirectoryIndex index.php
    Order allow,deny
    Allow from all
</Directory>

Log into http://yourdomain.com/squirrelmail to access it.