Manual tp Develop EAI Mail Server on CentOS 7

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EAI Email Server

This manual is designed to guide how to install an Email Server to send Thai email addresses or Email Address Internationalization (EAI) using Opensource Software. It could be further developed on different set of softwares.

Required Software

  1. Centos 7.4
  2. Postfix 3.2.3
  3. Dovecot 2.2.10
  4. MariaDB 10.3.11
  5. Squirrelmail 5.5.56


  • This manual have no explanation for installing Centos 7.4
  • Postfix Version 3.x.x and above will support EAI
  • In real setting, DNS server is also required
  • putty and winscp are used for connecting to the server

Installing EAI Email Server

1. Setting hostname

1. Update mail server packages to the latest version

# yum -y update

2. Define a hostname, e.g. with command

# hostnamectl set-hostname

3. Add the defined hostname to "hosts" file

# vi /etc/hosts

sample of hosts file   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

*Depends on the environment of CenOS installation, you may need to install additional services e.g. you may not be able to use "vi" command

4. Install wget to download additional necessary softwares

# yum -y install wget

5. Install telnet to test email server functionality

# yum -y install telnet

2. Setting firewall

1. Verify "firewalld service" status on the mail server

  • It must be active (running)
# systemctl status firewalld


Active: active (running) since Mon 2019-11-18 14:12:03 +07; 1h 13min ago

2. Check the firewall zone and network interface that are opened

# firewall-cmd --get-active-zones


interfaces: ens32

3. Check services of firewall in public zone

# firewall-cmd --zone=public --list-services


 cockpit dhcpv6-client ssh 

4. Open firewall services at public zone of mail server (open on services that needed)

# firewall-cmd --permanent --zone=public --add-service=http
# firewall-cmd --permanent --zone=public --add-service=https
# firewall-cmd --permanent --zone=public --add-service=mysql
# firewall-cmd --permanent --zone=public --add-service=smtp
# firewall-cmd --permanent --zone=public --add-service=smtps
# firewall-cmd --permanent --zone=public --add-service=imap
# firewall-cmd --permanent --zone=public --add-service=imaps
# firewall-cmd --reload

5. Check services list of the firewall at the public zone again, will find the just open services

*ref: configure firewall services for mail server (

# firewall-cmd --zone=public --list-services


 cockpit dhcpv6-client http https imap imaps mysql smtp smtps ssh  

6. In this example, we open SELinux for convenience in setting up (it is not recommended for production server)

  • เปลี่ยน SELinux=enforcing เป็น SELinux=disabled
# vi /etc/selinux/config


# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#       enforcing - SELinux security policy is enforced.
#       permissive - SELinux prints warnings instead of enforcing.
#       disabled - No SELinux policy is loaded.
# SELINUXTYPE= can take one of these two values:
#       targeted - Targeted processes are protected,
#       mls - Multi Level Security protection.

7. ตรวจสอบสถานะ SELinux อีกครั้ง

  • สั่ง restart server และทำการตรวจสอบ
# reboot
# sestatus



3. Create an SSL Cert

  • The step is for creating SSL key for using with postfix and dovecot

1. Create a private key

# cd /etc/pki/tls/certs
# make eai.key 


umask 77 ; \
/usr/bin/openssl genrsa -aes128 2048 > eai.key
Generating RSA private key, 2048 bit long modulus
e is 65537 (0x10001)
Enter pass phrase: #set passphrase
Verifying - Enter pass phrase:  #confirm 

2. Remove Passphase from the created private key

# openssl rsa -in eai.key -out eai.key 


Enter pass phrase for eai.key:  #input passphrase
writing RSA key

3. Create csr

# make eai.csr


umask 77 ; \
/usr/bin/openssl req -utf8 -new -key eai.key -out eai.csr
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
Country Name (2 letter code) [XX]:TH		#country
State or Province Name (full name) []:Bangkok		   #state
Locality Name (eg, city) [Default City]:Dusit		#city
Organization Name (eg, company) [Default Company Ltd]:EAI  	#company
Organizational Unit Name (eg, section) []:IT  	 #department
Common Name (eg, your name or your server's hostname) []  	 #server's FQDN
Email Address []		#email address
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:		#Enter
An optional company name []:		#Enter 

4. Generate key

# openssl x509 -in eai.csr -out eai.crt -req -signkey eai.key -days 3650


Signature ok
subject=/C=JP/ST=Hiroshima/L=Hiroshima/O=GTS/OU=Server World/
Getting Private key

4. Install mariadb, Postfix and Dovecot

1. Install mariadb , Postfix , Dovecot and necessary packages

# yum --enablerepo=centosplus install postfix
# yum install dovecot mariadb-server dovecot-mysql

2. Udate postfix version 2.x.x to version 3.x.x

  • On CentOS 7 postfix version 2.x.x is the default installation. We have to removepostfix version 2.x.x and upgrade to version 3.x.x or higher version
# yum -y remove postfix
# yum -y remove ssmtp
# yum -y remove sendmail
  • Create repo file gf.repo to install postfix version 3.x.x or above
# vi /etc/yum.repos.d/gf.repo


name=Ghettoforge packages that won't overwrite core distro packages.
name=Ghettoforge packages that will overwrite core distro packages.
# Please read *before* enabling this repository!
  • Load key to use with repo, put into path : /etc/pki/rpm-gpg/
# cd /etc/pki/rpm-gpg/
# wget
  • Install postfix version 3.x.x
# yum -y install postfix3 postfix-mysql
  • Chaeck postfix version 3.x.x
# postconf -d | grep mail_version
 mail_version = 3.5.7

3. Setup mariadb, postfix, dovecot to start automatically

# systemctl start mariadb
# systemctl enable mariadb
# systemctl start postfix
# systemctl enable postfix
# systemctl start dovecot
# systemctl enable dovecot

4. Check status of mariadb, postfix, dovecot

# systemctl status mariadb
# systemctl status postfix
# systemctl status dovecot

5. Setup MariaDB

1. Set UTF8 for mysql to accept Unicode by adding the following command to /etc/my.cnf.d/maridb-server.cnf under [mysqld]

# vi /etc/my.cnf


character-set-server = utf8
collation-server = utf8_general_ci
# Disabling symbolic-links is recommended to prevent assorted security risks
# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under a different user or group,
# customize your systemd unit file for mariadb according to the
# instructions in


# include all files from the config directory
!includedir /etc/my.cnf.d

2. Restart MariaDB

# systemctl restart mariadb

3. Set security access to mysql by setup password for root user (* define only new password, skip the rest by pressing enter)

#  mysql_secure_installation

4. Login to mysql using the new password

# mysql -u root -p

5. Create new DB for keeping records of Email Server usage

# USE eaimail;

Create a user with grants to the eaimail database

# GRANT SELECT, INSERT, UPDATE, DELETE ON eaimail.* TO 'yourdbuser'@'localhost' IDENTIFIED BY 'yourdbpassword';
# GRANT SELECT, INSERT, UPDATE, DELETE ON eaimail.* TO 'yourdbuser'@'localhost.localdomain' IDENTIFIED BY 'yourdbpassword';

7. Check the created user

# SHOW GRANTS FOR 'yourdbuser'@'localhost';

8. Create tables for domains, forwardings (to forward EAI email to ASCII email address), and users for creating mailboxes

# CREATE TABLE domains (domain varchar(50) NOT NULL, PRIMARY KEY (domain) );

8. Create tables for domains, forwardings (to forward EAI email to ASCII email address), and users for creating mailboxes

# CREATE TABLE forwardings (source varchar(80) NOT NULL, destination TEXT NOT NULL, PRIMARY KEY (source) );

8. Create tables for domains, forwardings (to forward EAI email to ASCII email address), and users for creating mailboxes

# CREATE TABLE users (email varchar(80) NOT NULL, password varchar(20) NOT NULL, PRIMARY KEY (email) );
# quit

11. Restart MariaDB

# systemctl restart mariadb

12. Setup domain and user in eaimail database

  • Access mariadb and choose eaimail database , enter ASCII domainand IDN , enter ASCII and EAI Email-Account with password to start
# mysql -u root -p
# USE eaimail;
# INSERT INTO domains (domain) VALUES ('');
# INSERT INTO domains (domain) VALUES ('อีเอไอ.ไทย');
# INSERT INTO users (email, password) VALUES ('', ENCRYPT('thaiuserpassword'));
# INSERT INTO users (email, password) VALUES ('ไทย@อีเอไอ.ไทย', ENCRYPT('thaiuserpassword'));
  • Setup a forwrding rule to forward all emails to EAI email address to ASCII email address, since the server can creat mailboxes in Unicode
# INSERT INTO forwardings (source,destination) VALUES ('ไทย@อีเอไอ.ไทย','');
# quit

6. Setup Postfix

Create connect file between Postfix and MariaDB

1. Create a script file to get domain value from DB

# vi /etc/postfix/


user = yourdbuser
password = yourdbpassword
dbname = eaimail
query = SELECT domain AS virtual FROM domains WHERE domain='%s' 
hosts = 

2. Create a file to retreive the forward email fron database

# vi /etc/postfix/


user = yourdbuser
password = yourdbpassword
dbname = eaimail
query = SELECT destination FROM forwardings WHERE source='%s' 
hosts =

3. Create a script file for creating mailbox and use for login

# vi /etc/postfix/


user = yourdbuser 
password = yourdbpassword
dbname = eaimail
query = SELECT CONCAT(SUBSTRING_INDEX(email,'@',-1),'/',SUBSTRING_INDEX(email,'@',1),'/') FROM users WHERE email='%s' 
hosts =

4. Create a script file for forwarding all email to another SMTP server (in the case that referring to a host as an IP address)

# vi /etc/postfix/


user = yourdbuser
password = yourdbpassword
dbname = eaimail
query = SELECT email FROM users WHERE email='%s' 
hosts =

5. Set access control right to the created script

# chmod o= /etc/postfix/mysql-virtual_*.cf
# chgrp postfix /etc/postfix/mysql-virtual_*.cf

6. Create user and group for the mailbox

# groupadd -g 5000 vmail 
# useradd -g vmail -u 5000 vmail -d /home/vmail -m

7. Modify "/etc/postfix/"

# vi /etc/postfix/


inet_interfaces = all
inet_protocols = ipv4
mydestination =  localhost, localhost.localdomain
alias_database = hash:/etc/aliases
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
meta_directory = /etc/postfix
shlib_directory = no
myhostname =
mydomain =
myorigin = $mydomain
readme_directory = no
mynetworks =
message_size_limit = 30720000
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_authenticated_header = yes
broken_sasl_auth_clients = yes
smtpd_use_tls = yes
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
smtpd_tls_cert_file = /etc/pki/tls/certs/eai.crt
smtpd_tls_key_file = /etc/pki/tls/certs/eai.key
smtpd_tls_security_level = may
smtpd_tls_auth_only = yes
smtpd_tls_loglevel = 1
alias_maps = hash:/etc/aliases	
virtual_mailbox_base = /home/vmail
virtual_mailbox_maps = proxy:mysql:/etc/postfix/
virtual_mailbox_domains = proxy:mysql:/etc/postfix/
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
virtual_alias_domains = อีเอไอ.ไทย
virtual_transport = dovecot
virtual_alias_maps = proxy:mysql:/etc/postfix/, mysql:/etc/postfix/
smtputf8_enable = yes
proxy_read_maps = $local_recipient_maps $mydestination $virtual_alias_maps $virtual_alias_domains $virtual_mailbox_maps $virtual_mailbox_domains $relay_recipient_maps $relay_domains $canonical_maps $sender_canonical_maps $recipient_canonical_maps $relocated_maps $transport_maps $mynetworks

8. Modify /etc/postfix/ add command to the end of the file

# vi /etc/postfix/


dovecot   unix  -       n       n       -       -       pipe
    flags=DRhu user=vmail:vmail argv=/usr/libexec/dovecot/deliver -f ${sender} -d ${recipient}

9. Modify /etc/postfix/ allow the commands below (others keep # in front)


smtps     inet  n       -       -       -       -       smtpd
		-o syslog_name=postfix/smtps
		-o smtpd_tls_wrappermode=yes
		-o smtpd_sasl_auth_enable=yes
		-o smtpd_client_restrictions=permit_sasl_authenticated,reject
		-o smtpd_relay_restrictions=permit_sasl_authenticated,reject
		-o milter_macro_daemon_name=ORIGINATING

10. restart postfix


# systemctl restart postfix

11. Define alias email by modifying the aliases file

  • add 2 lines
# vi /etc/aliases
postmaster: root

12. Update aliases and restart postfix

# newaliases
# systemctl restart postfix

7. Setup Dovecot

1. keep exisiting configuration

# mv /etc/dovecot/dovecot.conf /etc/dovecot/dovecot.conf-backup

2. Setup config dovecot

# vi /etc/dovecot/dovecot.conf


protocols = imap pop3 lmtp
log_timestamp = "%Y-%m-%d %H:%M:%S "
mail_location = maildir:/home/vmail/%d/%n/Maildir

ssl_cert = </etc/pki/tls/certs/eai.crt
ssl_key = </etc/pki/tls/certs/eai.key
ssl_dh_parameters_length = 2048 
ssl_cipher_list = ALL:!LOW:!SSLv2:!EXP:!aNULL
namespace {
    type = private
    separator = .
    prefix = INBOX.
    inbox = yes
service auth {
    unix_listener auth-master {
        mode = 0600
        user = vmail
    unix_listener /var/spool/postfix/private/auth {
        mode = 0666
        user = postfix
        group = postfix
user = root
auth_mechanisms = plain login
service auth-worker {
    user = root
protocol lda {
    log_path = /home/vmail/dovecot-deliver.log
    auth_socket_path = /var/run/dovecot/auth-master
    postmaster_address =
protocol pop3 {
    pop3_uidl_format = %08Xu%08Xv
        pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
passdb {
    driver = sql
    args = /etc/dovecot/dovecot-sql.conf.ext
userdb {
    driver = static
    args = uid=5000 gid=5000 home=/home/vmail/%d/%n allow_all_users=yes

3. Create script to let dovecot work with SQL

# vi /etc/dovecot/dovecot-sql.conf.ext


driver = mysql
connect = host= dbname=eaimail user=yourdbuser password=yourdbpassword
default_pass_scheme = CRYPT
password_query = SELECT email as user, password FROM users WHERE email='%u';

4. Allow users in the dovecot group to use

# chgrp dovecot /etc/dovecot/dovecot-sql.conf.ext
# chmod o= /etc/dovecot/dovecot-sql.conf.ext

5. restart dovecot

# systemctl restart dovecot

6. Check log of mail server at /var/log/maillog

# tail /var/log/maillog


Mar 18 17:10:26 localhost postfix/postfix-script[3274]: starting the Postfix mail system
Mar 18 17:10:26 localhost postfix/master[3276]: daemon started -- version 2.10.1, configuration /etc/postfix
Mar 18 17:12:28 localhost dovecot: master: Dovecot v2.2.10 starting up for imap, pop3 (core dumps disabled)

8. Test EAI Email Server

1. Test pop3

# telnet localhost pop3


Connected to localhost.localdomain.
Escape character is '^]'.
+OK Dovecot ready.

2. Test SMTP

# telnet localhost 25
# ehlo localhost

250-SIZE 30720000

3. Test sending and receiving emails with mailx

  • check log /var/log/maillog should get the result
# yum -y install mailx
# mailx (input subject then press enter follow by content and use  Ctrl+D for sending out)
# tail /var/log/maillog


Nov 13 15:19:07 mail postfix/pickup[31954]: E9AB020199E5: uid=0 from=<root>
Nov 13 15:19:07 mail postfix/cleanup[1938]: E9AB020199E5: message-id=<>
Nov 13 15:19:07 mail postfix/qmgr[21141]: E9AB020199E5: from=<>, size=434, nrcpt=1 (queue active)
Nov 13 15:19:08 mail postfix/pipe[1946]: E9AB020199E5: to=<>, relay=dovecot, delay=0.09, delays=0.04/0.01/0/0.03, dsn=2.0.0, status=sent (delivered via dovecot service)
Nov 13 15:19:08 mail postfix/qmgr[21141]: E9AB020199E5: removed
    • If found log error: unsupported dictionary type: MySQL, it is because of using postfix 3.2.4 which still has some bugs. If the problem comes from, check /etc/postfix/
# cd /etc/postfix/
# vi
mysql /usr/lib/postfix/ dict_mysql_open

4. Check the log to see Dovecot sending result /home/vmail/dovecot-deliver.log, should see the result

# tail /home/vmail/dovecot-deliver.log
2017-11-13 15:19:08 lda( Info: msgid=<>: saved mail to INBOX

5. Check the mailbox. When there are sendings and receiving emails, you will see the results

# cd /home/vmail/
# find



6. Check mailbox by using mail client, mutt, to see emaila inside the mailbox

# yum -y install mutt
# mutt -f .

7. Test sending an EAI mails

  • Use “.” to end and sending the message
  • Press Ctrl+] to quit
# telnet localhost 25
# EHLO localhost
# MAIL FROM: ไทย@อีเอไอ.ไทย SMTPUTF8			
# RCPT TO: ธนากานต์@คน.ไทย
# data
# Subject: eai test
# เทสอีเมลส์ภาษาไทย
# .

9. Install SquirrelMail

1. Install squirrelmail

# yum -y install epel-release
# yum install squirrelmail

2. If Apache was not install, install the Apche

# yum -y install httpd
# systemctl enable httpd
# systemctl start httpd
# systemctl status httpd

3. Copy/move squirrelmail to /var/www/html/

# cd /var/www/html/

(copy squirrelmail to /var/www/html/ , we use winscp to copy)

4. Create data directory for squirrelmail

# cd /var/lib/squirrelmail/
# mkdir data
# chmod ugo+rwx data/

5. Test login to access via web browsers Use the IP of Server follows by /squirrelmail e.g.

# Test sending and receiving mail