Description :

This article describes how to setup a mail server in centos 6

Here three popular packages used for configuration

• Postfix ( for sending )
• Dovecot ( for receiving )
• Squirrelmail ( for webmail access )

Installing and configuring postfix 

Step 1 : Before installation assign a static ip and add a host entry for your domain to that IP in the /etc/hosts

123.45.67.89 domainname.com

Step 2 : Issue the below command to install postfix

[root@mail ~]# yum -y install postfix

Step 3 : Now issue the below command to install SMTP AUTH packages

[root@mail ~]# yum -y install cyrus-sasl cyrus-sasl-devel cyrus-sasl-gssapi cyrus-sasl-md5 cyrus-sasl-plain

Postfix package installation is completed.

Step 4 : Issue the below commands one by one for creating SSL Certificate.

[root@mail ~]# mkdir /etc/postfix/ssl
[root@mail ~]# cd /etc/postfix/ssl/
[root@mail ssl]# openssl genrsa -des3 -rand /etc/hosts -out smtpd.key 1024
[root@mail ssl]# chmod 600 smtpd.key
[root@mail ssl]# openssl req -new -key smtpd.key -out smtpd.csr
[root@mail ssl]# openssl x509 -req -days 365 -in smtpd.csr -signkey smtpd.key -out smtpd.crt
[root@mail ssl]# openssl rsa -in smtpd.key -out smtpd.key.unencrypted
[root@mail ssl]# mv -f smtpd.key.unencrypted smtpd.key
[root@mail ssl]# openssl req -new -x509 -extensions v3_ca -keyout cakey.pem -out cacert.pem -days 365

Step 5 : Now open /etc/postfix/main.cf file.

Find and comment the below lines.

#inet_interfaces = localhost #---> line no 116
#mydestination = $myhostname, localhost.$mydomain, localhost #--> line no 164

and add these lines at the bottom of the file.

myhostname = mail.domainname.com
mydomain = domainname.com
myorigin = $mydomain
home_mailbox = mail/
mynetworks = 127.0.0.0/8
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = cyrus
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_sasl_authenticated_header = yes
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
smtpd_tls_auth_only = no
smtp_use_tls = yes
smtpd_use_tls = yes
smtp_tls_note_starttls_offer = yes
smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key
smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt
smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom

Step 6 : Now open /etc/postfix/master.cf file and add the below line after smt

smtps inet n - n - - smtpd
-o smtpd_sasl_auth_enable=yes
-o smtpd_reject_unlisted_sender=yes
-o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
-o broken_sasl_auth_clients=yes

Step 7 : Now start postfix and saslauthd service

[root@mail ~]# service postfix start

[root@mail ~]# service saslauthd start

Enter the below commands to start the postfix and saslauthd at startup

[root@mail ~]# chkconfig --level 235 postfix on

[root@mail ~]# chkconfig --level 235 saslauthd on

Step 8 : Now check your smtp connectivity . just telnet localhost on port 25 and type this command ehlo localhost

[root@mail ~]# telnet localhost 25
Trying ::1...
Connected to localhost.
Escape character is '^]'.
220 mail.domainname.com ESMTP Postfix
ehlo localhost <---- type this command 
250-mail.domainname.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
quit
221 2.0.0 Bye
Connection closed by foreign host.

Installing and configuring dovecot : 

Step 9 : Issue this command to install dovecot

[root@mail ~]# yum -y install dovecot

Step 10 : After installation open /etc/dovecot/dovecot.conf file and add the below line at the end of the file.
Make sure mail_location and home_mailbox in postfix configuration are using the same name.

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

Step 11 : Now start dovecot service

[root@mail ~]# service dovecot start

Enter the below command to start the dovecot at startup

[root@mail ~]# chkconfig --level 235 dovecot on

Step 12 : Now test your pop3 connectivity.

[root@mail ~]# telnet localhost 110
Trying ::1...
Connected to localhost.
Escape character is '^]'.
+OK Dovecot ready.
quit
+OK Logging out
Connection closed by foreign host.

Now the server is ready to receive mails.

Creating users and testing : 

Step 13 : Now create users to test your configuration.

[root@mail ~]# useradd -m user1 -s /sbin/nologin

[root@mail ~]# useradd -m user2 -s /sbin/nologin

and create passwords for the users created

[root@mail ~]# passwd user1

[root@mail ~]# passwd user2

Step 14 : Test your configuration in thunderbird.
Refer the below image for configuration details.

Step 15 : Now you can send and receive mails using this server. In case of any issues please check the log file
/var/log/maillog )

Now mail server is ready to use

Installing and configuring squirrelmail : 

Step 16 : We need to add EPEL repository to install squirrelmail package.

[root@mail ~]# rpm -ivh http://ftp.jaist.ac.jp/pub/Linux/Fedora/epel/6/i386/epel-release-6-8.noarch.rpm

Step 17 : Issue the below command to install squirrelmail.

[root@mail ~]# yum install squirrelmail

This command will install squirrelmail along with apache and php.

Step 18 : Now run the below command to configure squirrelmail .

[root@mail ~]# perl /usr/share/squirrelmail/config/conf.pl

=> 1 => domain (type Organization name) => R (return)
=> 2 => 1 => ( hit space for empty Domain name ) => choose 3 => SMTP ( choose SMTP ) => R (return)

=> D => dovecot (tyoe) => Press enter with default

=> s (save and quit)

Step 19 : Open /etc/httpd/conf.d/squirrelmail.conf file and uncomment below lines

# RewriteCond %{HTTPS} !=on
# RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

Step 20 : Start apache service

[root@mail ~]# service httpd start

Enter the below commands to start the httpd at startup

[root@mail ~]# chkconfig --level 235 httpd on

Step 21 : Now open http://serverip/webmail path in your browser.

and after login

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