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ISP Style Virtual Mail System

Written by Chris Gountanis

This document will explain the process of installing a fully working virtual email system on CentOS Linux using PostFix and Dovecot. I personally finalized my setup with RoundCube Webmail Project for robust online email usage. This how-to is very simple and easy to implement for beginners.

INSTALLATION NOTES

If you have not installed the packages this would be a good time to get moving. Using CentOS or RedHat Enterprise Linux (RHEL) you can use the “YUM” package manager to achieve this. You can also remove sendmail because it may cause SMTP based port issues with Postfix. Installing Postfix with database support is a bit tricky. You have to enable the CentOS Plus repository. You will then use upgrade if already installed or install for a full fresh install. I had to use upgrade due to installing the normal Postfix later finding out it would not work with this setup due to the lack of MySQL database support.

yum --enablerepo=centosplus upgrade/install postfix*

yum install dovecot

Note: You don't want to screw up your PostFix install with yum updates! Here is how to setup /etc/yum.repos.d/CentOS-Base.repo:

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
includepkgs=postfix-*
exclude=postfix-*plus*

You would also want to add this to both the [base] and [update] sections of /etc/yum.repos.d/CentOS-Base.repo, so as not to get postfix packages from there anymore:

exclude=postfix-*

If you had everything working and all of a sudden your SMTP is broke or you have error like "unsupported dictionary type: mysql" check this out for a nice easy fix.

DATABASE

The next step is to manually create the blank database with a corresponding user. You need to log into MySQL and create the database using the create database command. Then, give your new user permissions to that database. In this example the user is named mail with a password of mail.

mysql -uroot –p

CREATE DATABASE mail;

GRANT ALL PRIVILEGES ON mail.* TO 'mail'@'localhost' IDENTIFIED BY 'mail';

quit

The next step is to prepare the database. In this example we use MySQL with the PostFix Admin database dump provided with PostFix Admin files. Note the URL might change based on version. Extract the files to your web folder unless you plan on administering your email accounts manually. Something like phpMyAdmin would work as well once you understand the required table data.

wget http://sourceforge.net/projects/postfixadmin/

tar xvfz postfixadmin-2.1.0.tgz

Open postfixadmin-2.1.0/DATABASE_MYSQL.TXT with your favorite editor such as vim, nano or gedit and comment out or remove all lines under create user section Postfix / MySQL, since we have created our own use for the mail server. When this is done, just load the file into MySQL using the following command.

mysql -umail -p mail < postfixadmin-2.1.0/DATABASE_MYSQL.TXT

DOVECOT

Open up your Dovecot.conf for editing. The sample below is what I used to create this system using IMAP for webmail and POP3 for email clients like Outlook or Thunderbird direct access.

base_dir = /var/run/dovecot/

protocols = imap pop3

protocol imap {

listen = *:143

}

protocol pop3 {

listen = *:110

}

log_timestamp = "%Y-%m-%d %H:%M:%S"

syslog_facility = mail

mail_location = maildir:/var/vmail/%d/%u

mail_extra_groups = mail

mail_debug = no

first_valid_uid = 150

last_valid_uid = 150

maildir_copy_with_hardlinks = yes

protocol imap {

login_executable = /usr/libexec/dovecot/imap-login

mail_executable = /usr/libexec/dovecot/imap

imap_max_line_length = 65536

}

protocol pop3 {

login_executable = /usr/libexec/dovecot/pop3-login

mail_executable = /usr/libexec/dovecot/pop3

pop3_uidl_format = %08Xu%08Xv

}

protocol lda {

postmaster_address = This e-mail address is being protected from spambots. You need JavaScript enabled to view it

sendmail_path = /usr/lib/sendmail

auth_socket_path = /var/run/dovecot/auth-master

}

auth_verbose = no

auth_debug = no

auth_debug_passwords = no

auth default {

mechanisms = plain

passdb sql {

args = /etc/dovecot/dovecot-sql.conf

}

userdb sql {

args = /etc/dovecot/dovecot-sql.conf

}

user = nobody

socket listen {

master {

path = /var/run/dovecot/auth-master

mode = 0660

user = vmail

group = mail

}

client {

path = /var/spool/postfix/private/auth

mode = 0660

user = postfix

group = postfix

}

Open up the dovecot-sql.conf for editing. This file has been specified in the main Dovecot configuration file. Dovecot looks for this file in order to fire up the database driven virtual mailboxes.

driver = mysql

connect = host=localhost dbname=mail user=mail password=mail

default_pass_scheme = MD5

user_query = SELECT '/var/vmail/%d/%n' as home, 'maildir:/var/vmail/%d/%n' as mail, 150 AS uid, 12 AS gid, concat('dirsize:storage=', quota) AS

quota FROM mailbox WHERE username = '%u' AND active = '1'

password_query = SELECT username as user, password, '/var/vmail/%d/%n' as userdb_home, 'maildir:/var/vmail/%d/%n' as userdb_mail, 150 as

userdb_uid, 12 as userdb_gid FROM mailbox WHERE username = '%u' AND active = '1'

POSTFIX

Open Main.cf for editing. You will need to change “hostname” and “myorigin”. The rest was simple and should work on almost all systems for simple implementation.

biff = no

append_dot_mydomain = no

#delay_warning_time = 4h

myhostname = yourhostnamehere like mail.domain.com

myorigin = 192.168.1.1

mydestination = localhost

relayhost =

alias_maps = hash:/etc/aliases

mynetworks = 127.0.0.0/8

mailbox_size_limit = 0

recipient_delimiter = +

inet_interfaces = all

smtp_helo_name = $myhostname

# Virtual mailbox settings

virtual_mailbox_domains = proxy:mysql:$config_directory/mysql_virtual_domains_maps.cf

virtual_mailbox_base = /var/vmail

virtual_mailbox_maps = proxy:mysql:$config_directory/mysql_virtual_mailbox_maps.cf

virtual_alias_maps = proxy:mysql:$config_directory/mysql_virtual_alias_maps.cf

virtual_minimum_uid = 150

virtual_uid_maps = static:150

virtual_gid_maps = static:12

virtual_transport = dovecot

dovecot_destination_recipient_limit = 1

# SASL Authentication

smtpd_sasl_auth_enable = yes

smtpd_sasl_exceptions_networks = $mynetworks

smtpd_sasl_security_options = noanonymous

broken_sasl_auth_clients = yes

smtpd_sasl_type = dovecot

smtpd_sasl_path = private/auth

smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, permit

Open master.cf for editing. Add these two lines to the bottom of the file. I found that if the proper spacing and formatting was not found Postfix would actually not start properly. So as a tip check these lines for proper spacing and formatting as a trouble shooting step.

dovecot unix - n n - - pipe

flags=DRhu user=vmail:mail argv=/usr/libexec/dovecot/deliver -d $(recipient)

Add file mysql_virtual_alias_maps.cf and open for editing.

user = mail

password = mail

hosts = localhost

dbname = mail

table = alias

select_field = goto

where_field = address

additional_conditions = and active = '1'

#query = SELECT goto FROM alias WHERE address='%s' AND active = '1'

Add file mysql_virtual_domains_maps.cf and open for editing.

user = mail

password = mail

hosts = localhost

dbname = mail

table = domain

select_field = domain

where_field = domain

additional_conditions = and backupmx = '0' and active = '1'

#query = SELECT domain FROM domain WHERE domain='%s' AND backupmx = '0' AND active = '1'

Add file mysql_virtual_mailbox_limit_maps.cf and open for editing.

user = mail

password = mail

hosts = localhost

dbname = mail

table = mailbox

select_field = quota

where_field = username

additional_conditions = and active = '1'

#query = SELECT quota FROM mailbox WHERE username='%s' AND active = '1'

Add file mysql_virtual_mailbox_maps.cf and open for editing.

user = mail

password = mail

hosts = localhost

dbname = mail

table = mailbox

select_field = CONCAT(domain,'/',maildir)

where_field = username

additional_conditions = and active = '1'

#query = SELECT CONCAT(domain,'/',maildir) FROM mailbox WHERE username='%s' AND active = '1'

ADMINISTRATION

I have installed phpMyAdmin as well as Postfix Admin. Between the two packages I was able to learn how to create mailboxes manually, if needed. I suggest you start with tools like Postfix Admin until you fully understand what data is required for your email system to function properly.

WEBMAIL

I decided to go with RoundCube Webmail Project due to the sleek look and feel. Once downloaded and extracted it took all of 15 minutes to have it up and running for all users globally. If you want to really seal the deal create a virtual host within Apache to handle webmail.* for all of your domains. This really gives it a professional touch for your end users.

CONCLUSION

Since installing the system I have had no issues with many domains containing multiple virtual user mailboxes. This is a great virtual setup and can easily go hand in hand with my virtual ftp documentation posted earlier. Once you have these down, you can easily add virtual hosts in Apache for a robust hosting solution at no required software cost.

EXTRAS

Postfix Admin http://postfixadmin.sourceforge.net/

phpMyAdmin http://www.phpmyadmin.net/

Roundcube Webmail Project http://roundcube.net/

Last Updated on Wednesday, 24 September 2008 21:30