Virtual Users And Domains With Postfix, Courier And MySQL (CentOS 5.1) - Page 2

7 Create The MySQL Database For Postfix/Courier

We create a database called mail:

mysqladmin -u root -p create mail

Next, we go to the MySQL shell:

mysql -u root -p

On the MySQL shell, we create the user mail_admin with the passwort mail_admin_password (replace it with your own password) who has SELECT,INSERT,UPDATE,DELETE privileges on the mail database. This user will be used by Postfix and Courier to connect to the mail database:

GRANT SELECT, INSERT, UPDATE, DELETE ON mail.* TO 'mail_admin'@'localhost' IDENTIFIED BY 'mail_admin_password';
GRANT SELECT, INSERT, UPDATE, DELETE ON mail.* TO 'mail_admin'@'localhost.localdomain' IDENTIFIED BY 'mail_admin_password';

Still on the MySQL shell, we create the tables that Postfix and Courier need:

USE mail;

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

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

email varchar(80) NOT NULL,
password varchar(20) NOT NULL,
quota INT(10) DEFAULT '10485760',

CREATE TABLE transport (
domain varchar(128) NOT NULL default '',
transport varchar(128) NOT NULL default '',
UNIQUE KEY domain (domain)


As you may have noticed, with the quit; command we have left the MySQL shell and are back on the Linux shell.

The domains table will store each virtual domain that Postfix should receive emails for (e.g.


The forwardings table is for aliasing one email address to another, e.g. forward emails for [email protected] to [email protected].

source destination
[email protected] [email protected]

The users table stores all virtual users (i.e. email addresses, because theemail address and user name is the same) and passwords (in encrypted form!) and a quota value for each mail box (in this example the default value is 10485760 bytes which means 10MB).

email password quota
[email protected] No9.E4skNvGa. ("secret" in encrypted form) 10485760

The transport table is optional, it is for advanced users. It allows to forward mails for single users, whole domains or all mails to another server. For example,

domain transport smtp:[]

would forward all emails for via the smtp protocol to the server with the IP address (the square brackets [] mean "do not make a lookup of the MX DNS record" (which makes sense for IP addresses...). If you use a fully qualified domain name (FQDN) instead you would not use the square brackets.).


8 Configure Postfix

Now we have to tell Postfix where it can find all the information in the database. Therefore we have to create six text files. You will notice that I tell Postfix to connect to MySQL on the IP address instead of localhost. This is because Postfix is running in a chroot jail and does not have access to the MySQL socket which it would try to connect if I told Postfix to use localhost. If I use Postfix uses TCP networking to connect to MySQL which is no problem even in a chroot jail (the alternative would be to move the MySQL socket into the chroot jail which causes some other problems).

Now let's create our six text files.

vi /etc/postfix/

user = mail_admin
password = mail_admin_password
dbname = mail
query = SELECT domain AS virtual FROM domains WHERE domain='%s'
hosts =

vi /etc/postfix/

user = mail_admin
password = mail_admin_password
dbname = mail
query = SELECT destination FROM forwardings WHERE source='%s'
hosts =

vi /etc/postfix/

user = mail_admin
password = mail_admin_password
dbname = mail
query = SELECT CONCAT(SUBSTRING_INDEX(email,'@',-1),'/',SUBSTRING_INDEX(email,'@',1),'/') FROM users WHERE email='%s'
hosts =

vi /etc/postfix/

user = mail_admin
password = mail_admin_password
dbname = mail
query = SELECT email FROM users WHERE email='%s'
hosts =

vi /etc/postfix/

user = mail_admin
password = mail_admin_password
dbname = mail
query = SELECT transport FROM transport WHERE domain='%s'
hosts =

vi /etc/postfix/

user = mail_admin
password = mail_admin_password
dbname = mail
query = SELECT quota FROM users WHERE email='%s'
hosts =

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

Now we create a user and group called vmail with the home directory /home/vmail. This is where all mail boxes will be stored.

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

Next we do some Postfix configuration. Go sure that you replace with a valid FQDN, otherwise your Postfix might not work properly!

postconf -e 'myhostname ='
postconf -e 'mydestination =, localhost, localhost.localdomain'
postconf -e 'mynetworks ='
postconf -e 'virtual_alias_domains ='
postconf -e ' virtual_alias_maps = proxy:mysql:/etc/postfix/, mysql:/etc/postfix/'
postconf -e 'virtual_mailbox_domains = proxy:mysql:/etc/postfix/'
postconf -e 'virtual_mailbox_maps = proxy:mysql:/etc/postfix/'
postconf -e 'virtual_mailbox_base = /home/vmail'
postconf -e 'virtual_uid_maps = static:5000'
postconf -e 'virtual_gid_maps = static:5000'
postconf -e 'smtpd_sasl_auth_enable = yes'
postconf -e 'broken_sasl_auth_clients = yes'
postconf -e 'smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination'
postconf -e 'smtpd_use_tls = yes'
postconf -e 'smtpd_tls_cert_file = /etc/postfix/smtpd.cert'
postconf -e 'smtpd_tls_key_file = /etc/postfix/smtpd.key'
postconf -e 'transport_maps = proxy:mysql:/etc/postfix/'
postconf -e 'virtual_create_maildirsize = yes'
postconf -e 'virtual_maildir_extended = yes'
postconf -e 'virtual_mailbox_limit_maps = proxy:mysql:/etc/postfix/'
postconf -e 'virtual_mailbox_limit_override = yes'
postconf -e 'virtual_maildir_limit_message = "The user you are trying to reach is over quota."'
postconf -e 'virtual_overquota_bounce = yes'
postconf -e '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 $virtual_mailbox_limit_maps'
postconf -e 'inet_interfaces = all'

Afterwards we create the SSL certificate that is needed for TLS:

cd /etc/postfix
openssl req -new -outform PEM -out smtpd.cert -newkey rsa:2048 -nodes -keyout smtpd.key -keyform PEM -days 365 -x509

Country Name (2 letter code) [GB]: <-- Enter your Country Name (e.g., "DE").
State or Province Name (full name) [Berkshire]:
<-- Enter your State or Province Name.
Locality Name (eg, city) [Newbury]:
<-- Enter your City.
Organization Name (eg, company) [My Company Ltd]:
<-- Enter your Organization Name (e.g., the name of your company).
Organizational Unit Name (eg, section) []:
<-- Enter your Organizational Unit Name (e.g. "IT Department").
Common Name (eg, your name or your server's hostname) []:
<-- Enter the Fully Qualified Domain Name of the system (e.g. "").
Email Address []:
<-- Enter your Email Address.

Then change the permissions of the smtpd.key:

chmod o= /etc/postfix/smtpd.key


9 Configure Saslauthd

Edit /usr/lib/sasl2/smtpd.conf. It should look like this:

vi /usr/lib/sasl2/smtpd.conf

pwcheck_method: authdaemond
log_level: 3
mech_list: PLAIN LOGIN

Then turn off Sendmail and start Postfix, saslauthd, and courier-authlib:

chmod 755 /var/spool/authdaemon
chkconfig --levels 235 courier-authlib on
/etc/init.d/courier-authlib start

chkconfig --levels 235 sendmail off
chkconfig --levels 235 postfix on
chkconfig --levels 235 saslauthd on
/etc/init.d/sendmail stop
/etc/init.d/postfix start
/etc/init.d/saslauthd start


10 Configure Courier

Now we have to tell Courier that it should authenticate against our MySQL database. First, edit /etc/authlib/authdaemonrc and change the value of authmodulelist so that it reads

vi /etc/authlib/authdaemonrc

#authmodulelist="authuserdb authpam authpgsql authldap authmysql authcustom authpipe"

Then edit /etc/authlib/authmysqlrc. It should look exactly like this (again, make sure to fill in the correct database details):

cp /etc/authlib/authmysqlrc /etc/authlib/authmysqlrc_orig
cat /dev/null > /etc/authlib/authmysqlrc
vi /etc/authlib/authmysqlrc

MYSQL_SERVER localhost
MYSQL_PASSWORD mail_admin_password
MYSQL_HOME_FIELD "/home/vmail"

Then restart Courier:

chkconfig --levels 235 courier-imap on
/etc/init.d/courier-authlib restart
/etc/init.d/courier-imap restart

By running

telnet localhost pop3

you can see if your POP3 server is working correctly. It should give back +OK Hello there. (type quit to get back to the Linux shell):

[root@server1 postfix]# telnet localhost pop3
Connected to localhost.localdomain (
Escape character is '^]'.
+OK Hello there.
+OK Better luck next time.
Connection closed by foreign host.
[root@server1 postfix]#

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From: at: 2008-04-06 14:05:34

This is a great mail setup, and I recommend it highly to anyone looking for a good, robust, easy to manage solution for providing different clients (i.e. domains) with mail.  I have used Fedora Core 5 version, and now the CentOS 5 versions.  I couldnt be happier, except....

In it's current form, if one user authenticates and sends an email via this server to another user on the same box (either same domain or different domain), it is likely they will be flagged as spam under one of the dynamic IP lookup rules - actually they are likely to be flagged under a number of rules, and will most likely exceed the spam level. 

The solution to this is to add another postfix setting in

smtpd_sasl_authenticated_header = yes

This has TOTALLY solved this BIG problem for me.  Refer to form more information - about half way down the page.

Falco - I recommend you incorporate this into the actual instructions above, and any other guide you are doing with Postfix 2.3+ and SpamAssassin 3.1.4+ .  Thanks for the guides - keep them coming.