This guide will show you how to setup an email server accessible using a POP3, IMAP or web browser client. It will also show you how to include virus scanning and spam tagging in the mail server. If you have an existing Active Directory or LDAP infrastructure, the last section will show you how to integrate it into your email server so you won’t have to maintain two sets of user accounts.

How to install Linux

You can use either Red Hat Enterprise Linux 5 or CentOS 5. RHEL 5 can be purchased from Red Hat and comes with support. CentOS 5 on the other hand can be downloaded here.

1. How to install CentOS 5.

2. How to setup CentOS 5.

To simplify our administration tasks, log in as the user root and specify your root password. This is not the recommended way of administering a Linux box, but for the tasks at hand it is the most efficient way.

How to install SMTP, POP3, IMAP and Webmail service

Postfix will be providing the SMTP service, Dovecot will provide the POP3 and IMAP service, while Apache and SquirrelMail will provide the Webmail service.

1. How to install and setup Postfix SMTP server.

2. How to install and setup Dovecot POP3 and IMAP server.

3. Configure Postfix SMTP Authentication using Dovecot SASL.

4. How to install and setup SquirrelMail WebMail.

5. How to configure the firewall.

How to create mailboxes, aliases and distribution groups

To create a mailbox, just create a new user account.

How to setup a mailing list or proxy address in Postfix.

How to add antivirus and antispam filtering

We will be using Clam AntiVirus for virus scanning, SpamAssassin for the spam tagging and MailScanner to integrate them into Postfix.

1. How to install MailScanner.

2. How to install Clam AntiVirus (ClamAV).

3. MailScanner, ClamAV, SpamAssassin and Postfix Integration Guide.

You can greatly reduce the volume of spam and viruses reaching your mail server if you are willing to give up something. If you are willing to have your mail delayed (time), install Postgrey. If you are willing to spend (money), get the Barracuda Spam Firewall.

How to integrate Active Directory/LDAP

Integrating Active Directory/LDAP into your mail server will turn your Linux email server into a lean and mean Exchange like machine. And you won’t have to deal with Linux system accounts or edit configuration files for common tasks like creating mailboxes and mailing lists. And finally, you can provide your users with standard address book.

Active Directory/LDAP virtual users in Postfix and Dovecot.

How to use the Active Directory Distribution Group in Postfix.

How to add Active Directory/LDAP into the SquirrelMail Addressbook.

Using Winbind to integrate Active Directory user accounts.
Another way to integrate Active Directory into your mail server. I highly recommend using the virtual user solution above instead of this one.

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For Windows users, you can use DeltaCopy. DeltaCopy includes the rsync console application and a client and server GUI.

Server

1. Edit the file /etc/rsyncd.conf and add the lines below.

[pub]
path=/home/public
read only=no

Replace pub with any directory name you prefer. The path on the other hand should point to a valid nobody readable and writeable directory.

2. Allow the rsync service to launch by enabling it in the On Demand Service in the Service Configuration tool. Learn more about the Service Configuration tool.

3. Open the rsync port 873 in the firewall. Learn how to configure the firewall.

Client

To transfer a file/directory, the basic command is rsync src dest. Below are some examples.

To get a file/directory from the server, type in

rsync rsync://server/pub/test.txt .

Replace server with the name of your server, pub with the name of your directory, test.txt with the name of a file or directory you wish to download and replace . with a path to your local directory if you do not want to save into your current directory.

To send a file/directory to the server, type in

rsync test.txt rsync://server/pub

Replace server with the name of your server, pub with the name of your directory, test.txt with the name of a file or directory you wish to upload.

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Generate a Private Key

Make sure you are logged in as the root user when doing steps below.

1. Generate a pass phrase protected private key using the command below. Provide a pass phrase when asked.

openssl genrsa -des3 -out localhost.key 1024

2. Remove the pass phrase protection using the command below. Provide the pass phrase when asked.

openssl rsa -in localhost.key -out localhost.key

3. Type in the command below to ensure that the private key will be readable by the root user only.

chmod 400 localhost.key

Generate a Certificate

1. Generate a certificate signing request by typing in the command below and filling in your host information.

openssl req -new -key localhost.key -out localhost.csr

Signing options

• For a publicly accessible site, have it signed by a reputable third party like Verisign
• For Active Directory intranets, you can sign it using the Microsoft Certificate Services. Learn how to submit a certificate request to the Microsoft Certificate Services.
• For intranets or testing sites, you can sign it yourself.

To self sign your certificate request, type in the command below.

openssl x509 -req -days 365 -in localhost.csr
 -signkey localhost.key -out localhost.crt

Configuring Apache for SSL

1. Move the file localhost.key into /etc/pki/tls/private/

mv localhost.key /etc/pki/tls/private/

2. Place the certificate file into /etc/pki/tls/certs/ and name the file as localhost.crt. The command below applies to self-signed certificate only.

mv localhost.crt /etc/pki/tls/certs/

3. Edit the file /etc/httpd/conf.d/ssl.conf and edit the lines below.

DocumentRoot = /usr/share/squirrelmail
ServerName = mail.acme.local:443

Replace mail.acme.local with your server name.

4. Restart the httpd service. Learn how to restart services here.

5. Try accessing SquirrelMail using https instead of http.

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To issue a certificate for a web server, make sure you have all of the items below.

• Domain administrator account
• Internet Explorer
• Windows server installed with Microsoft Certificate Services. Learn how to install Microsoft Certificate Services in Windows 2003 Server.

1. Launch Internet Explorer and connect to your Certificate Services server. The URL is http://server/certsrv, replace server with the name of your server. Next, click Request a certificate.

2. In the Request a Certificate page, click submit an advanced certificate request.

3. In the Advanced Certificate Request page, click Submit a certificate request by using a base-64-encoded CMC or PKCS #10 file or submit a renewal request by using a base-64-encoded PKCS#7 file.

4. In the Submit a Certificate Request or Renewal Request page, paste the content of the request file into the Base-64-encoded certificate request box. Select Web Server in the Certificate Template and click Submit.

5. In the Certificate Issued page, select Base 64 encoded and click Download certificate.

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1. Go to www.webmin.com and download the Webmin RPM package.

2. Double click the downloaded file to install Webmin.

3. After installing Webmin, configure the firewall to allow traffic on the TCP port 10000. Learn how to configure the firewall.

4. From web browser, connect to https://localhost:10000 and login using root.

5. That’s it. It’s working.

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Make sure that your host name is properly registered in your DNS or /etc/hosts file. Check if your hostname is registered properly by executing

ping mail.acme.local

in a terminal window, replace mail.acme.local with your own host name. If it returns 127.0.0.1 or unknown host that means it is not registered properly.

Installing Fedora Directory Server

1. Update your Red Hat Enterprise Linux or CentOS to 5.1.

2. Install Fedora Directory Server by typing in the commands below in a terminal window

cd /etc/yum.repos.d
wget www.linux-mail.info/files/fedora-ds.repo
yum install fedora-ds openldap-clients

3. Create a new user and group named fds. This account will be used to run the fds service. Learn how to create a new user.

4. Type in setup-ds-admin.pl in a terminal window to setup Fedora Directory Server. Most of the time, the default is simply accepted indicated by the ↵ in the sample session below.

[root@mail yum.repos.d]# setup-ds-admin.pl

==============================================================================
This program will set up the Fedora Directory and Administration Servers.

It is recommended that you have “root” privilege to set up the software.
Tips for using this program:
  - Press “Enter” to choose the default and go to the next screen
  - Type “Control-B” then “Enter” to go back to the previous screen
  - Type “Control-C” to cancel the setup program

Would you like to continue with set up? [yes]: ↵

==============================================================================
BY SETTING UP AND USING THIS SOFTWARE YOU ARE CONSENTING TO BE BOUND BY
AND ARE BECOMING A PARTY TO THE AGREEMENT FOUND IN THE
LICENSE.TXT FILE. IF YOU DO NOT AGREE TO ALL OF THE TERMS
OF THIS AGREEMENT, PLEASE DO NOT SET UP OR USE THIS SOFTWARE.

Do you agree to the license terms? [no]: yes

==============================================================================
Your system has been scanned for potential problems, missing patches,
etc.  The following output is a report of the items found that need to
be addressed before running this software in a production
environment.

Fedora Directory Server system tuning analysis version 10-AUGUST-2007.

NOTICE : System is i686-unknown-linux2.6.18-53.el5 (1 processor).

WARNING: 376MB of physical memory is available on the system. 1024MB is recommended for best performance on large production system.

NOTICE : The net.ipv4.tcp_keepalive_time is set to 7200000 milliseconds
(120 minutes).  This may cause temporary server congestion from lost
client connections.

WARNING: There are only 1024 file descriptors (hard limit) available, which
limit the number of simultaneous connections.  

WARNING: There are only 1024 file descriptors (soft limit) available, which
limit the number of simultaneous connections.  

Would you like to continue? [no]: yes

==============================================================================
Choose a setup type:

   1. Express
       Allows you to quickly set up the servers using the most
       common options and pre-defined defaults. Useful for quick
       evaluation of the products.

   2. Typical
       Allows you to specify common defaults and options.

   3. Custom
       Allows you to specify more advanced options. This is 
       recommended for experienced server administrators only.

To accept the default shown in brackets, press the Enter key.

Choose a setup type [2]: ↵

==============================================================================
Enter the fully qualified domain name of the computer
on which you’re setting up server software. Using the form
<hostname>.<domainname>
Example: eros.example.com.

To accept the default shown in brackets, press the Enter key.

Computer name [mail.acme.local]: ↵

==============================================================================
The servers must run as a specific user in a specific group.
It is strongly recommended that this user should have no privileges
on the computer (i.e. a non-root user).  The setup procedure
will give this user/group some permissions in specific paths/files
to perform server-specific operations.

If you have not yet created a user and group for the servers,
create this user and group using your native operating
system utilities.

System User [nobody]: fds
System Group [nobody]: fds

==============================================================================
Server information is stored in the configuration directory server.
This information is used by the console and administration server to
configure and manage your servers.  If you have already set up a
configuration directory server, you should register any servers you
set up or create with the configuration server.  To do so, the
following information about the configuration server is required: the
fully qualified host name of the form
<hostname>.<domainname>(e.g. hostname.example.com), the port number
(default 389), the suffix, the DN and password of a user having
permission to write the configuration information, usually the
configuration directory administrator, and if you are using security
(TLS/SSL).  If you are using TLS/SSL, specify the TLS/SSL (LDAPS) port
number (default 636) instead of the regular LDAP port number, and
provide the CA certificate (in PEM/ASCII format).

If you do not yet have a configuration directory server, enter ‘No’ to
be prompted to set up one.

Do you want to register this software with an existing
configuration directory server? [no]: ↵

==============================================================================
Please enter the administrator ID for the configuration directory
server.  This is the ID typically used to log in to the console.  You
will also be prompted for the password.

Configuration directory server
administrator ID [admin]: ↵
Password: 
Password (confirm): 

==============================================================================
The information stored in the configuration directory server can be
separated into different Administration Domains.  If you are managing
multiple software releases at the same time, or managing information
about multiple domains, you may use the Administration Domain to keep
them separate.

If you are not using administrative domains, press Enter to select the
default.  Otherwise, enter some descriptive, unique name for the
administration domain, such as the name of the organization
responsible for managing the domain.

Administration Domain [acme.local]: ↵

==============================================================================
The standard directory server network port number is 389.  However, if
you are not logged as the superuser, or port 389 is in use, the
default value will be a random unused port number greater than 1024.
If you want to use port 389, make sure that you are logged in as the
superuser, that port 389 is not in use.

Directory server network port [389]: ↵

==============================================================================
Each instance of a directory server requires a unique identifier.
This identifier is used to name the various
instance specific files and directories in the file system,
as well as for other uses as a server instance identifier.

Directory server identifier [mail]: ↵

==============================================================================
The suffix is the root of your directory tree.  The suffix must be a valid DN.
It is recommended that you use the dc=domaincomponent suffix convention.
For example, if your domain is example.com,
you should use dc=example,dc=com for your suffix.
Setup will create this initial suffix for you,
but you may have more than one suffix.
Use the directory server utilities to create additional suffixes.

Suffix [dc=acme, dc=local]: ↵

==============================================================================
Certain directory server operations require an administrative user.
This user is referred to as the Directory Manager and typically has a
bind Distinguished Name (DN) of cn=Directory Manager.
You will also be prompted for the password for this user.  The password must
be at least 8 characters long, and contain no spaces.

Directory Manager DN [cn=Directory Manager]: ↵
Password: 
Password (confirm): 

==============================================================================
The Administration Server is separate from any of your web or application
servers since it listens to a different port and access to it is
restricted.

Pick a port number between 1024 and 65535 to run your Administration
Server on. You should NOT use a port number which you plan to
run a web or application server on, rather, select a number which you
will remember and which will not be used for anything else.

Administration port [9830]: ↵

==============================================================================
The interactive phase is complete.  The script will now set up your
servers.  Enter No or go Back if you want to change something.

Are you ready to set up your servers? [yes]: ↵
Creating directory server . . .
Your new DS instance ‘mail’ was successfully created.
Creating the configuration directory server . . .
Beginning Admin Server creation . . .
Creating Admin Server files and directories . . .
Updating adm.conf . . .
Updating admpw . . .
Registering admin server with the configuration directory server . . .
Updating adm.conf with information from configuration directory server . . .
Updating the configuration for the httpd engine . . .
Starting admin server . . .
The admin server was successfully started.
Admin server was successfully created, configured, and started.
Exiting . . .
Log file is ‘/tmp/setupcT78dr.log’

[root@mail yum.repos.d]# 

5. Setup the Fedora Directory Server SSL by executing the commands below in a terminal window

wget directory.fedoraproject.org/download/setupssl2.sh
chmod +x setupssl2.sh
./setupssl2.sh /etc/dirsrv/slapd-mail

Replace mail with your own server instance. During setup, you will be asked for the password of directory manager.

6. Restart the dirsrv, dirsrv-admin and httpd service. Learn how to stop and start services here.

Administering Fedora Directory Server

1. Install the Java Runtime Environment from Sun Microsystem.

2. From a terminal window, type in fedora-idm-console. This will launch the Fedora Console Login window.

 

User ID

cn=directory manager

Password

the directory manager password

Administration URL

localhost:9830

 

The values above assumes you have used the default values.

3. Success.

Related Pages

Active Directory/LDAP virtual users in Postfix and Dovecot.

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Installing the Java Runtime Environment (JRE)

1. Download the Java software for Linux from Sun Microsystem. Choose the RPM format.

2. Right click the downloaded file and click Properties. This will launch the Properties window.

3. In the Properties window, click the Permissions tab and check Allow executing file as program. Click Close when you are done.

4. Double click the file to execute it and click Run in Terminal. Press Spacebar until you reach the end of the text. Type in yes and press Enter to agree to the license terms and proceed with the installation.

5. Check your Java installation by typing in the command below. Note down the version.

java -version

6. If the version being used is not the one you installed, type in the command below to make it so.

ln -sf /usr/java/default/bin/java /usr/bin/java

The above would be the case if you install the Fedora Directory Server which pulls in on an old version of Java during installation.

Configuring Firefox

1. Enable Firefox to find the Java plugin by typing in the commands below in a terminal window.

cd /usr/lib/mozilla/plugins
ln -sf /usr/java/default/plugin/i386/ns7/libjavaplugin_oji.so .

2. Launch Firefox and type in about:plugins in the address bar to verify the presence of Java.

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1. If you have not yet configured the RPMForge yum repository, see Add RPMForge to your Yum repository.

2. Type in yum install perl perl-ldap from a terminal window. This will install the ldap-chpasswd prerequisites.

3. Go to the /usr/share/squirrelmail/plugin/change_passwd directory. Check if ldap-chpasswd runs by typing in ./ldap-chpasswd

4. Copy the file ldap-chpasswd.cfg.sample and save it as ldap-chpasswd.cfg. Next edit the ldap-chpasswd.cfg file and set the value of the keys below.

$isActiveDirectory = 0;
$hosts = "localhost";
$domain = "acme.local";
$searchBase = "dc=acme,dc=local";
$bindDN = "cn=manager,dc=acme,dc=local";
$bindPW = "secret";
$userAttr = "uid";

Values above are samples only, replace them with values appropriate for your setup.

5. Check your configuration by typing in ./ldap-chpasswd user. Replace user and with a LDAP user name. You should see the distinguished name of the user.

6. Edit the config.php and set $overridePathToChpasswd to ldap-chpasswd. That’s it, you should now be able to change your LDAP password from SquirrelMail.

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1. If you have not yet configured the RPMForge yum repository, see Add RPMForge to your Yum repository.

2. Type in yum install perl perl-ldap from a terminal window. This will install the ldap-chpasswd prerequisites.

3. Go to the /usr/share/squirrelmail/plugin/change_passwd directory. Check if ldap-chpasswd runs by typing in ./ldap-chpasswd. You should see your autodetected settings.

4. Export a base-64 encoded certificate from your SSL enabled Active Directory server and place the file into this directory.

5. Copy the file ldap-chpasswd.cfg.sample and save it as ldap-chpasswd.cfg. Next edit the ldap-chpasswd.cfg file and set the value of $certificate to the name of the certificate file. If any of the autodetected settings are incorrect, you can specify the correct values here.

6. Check your configuration by typing in ./ldap-chpasswd user password. Replace user and password with a valid Active Directory user name and password. You should see the distinguished name of the user.

7. Edit the config.php and set $overridePathToChpasswd to ldap-chpasswd. That’s it, you should now be able to change your Active Directory password from SquirrelMail.

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1. Click Start, select Administrative Tools and click Certification Authority. This will launch the Certification Authority application.

2. Select a certification authority, press right click and click Properties.

3. In the Properties window, click the View Certificate button.

4. In the Certificate window, click the Details tab and click the Copy to File button.

5. Click Next in the Certificate Export Wizard window.

6. Select Base-64 encoded X.509 and click Next.

7. Specify the path and file name of the certificate and click Next.

8. Finally, click Finish to export the certificate.

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