Introduction

This howto will help you to have a basic Postfix mail server setup for your corporate environment. The main intention of this howto is to teach how you can install and configure a basic Postfix mail server setup with IMAP and POP3 services. I do not intend to tell you how you can integrate advanced stuffs like virus checking and spam filtering with this guide. My advanced postfix guide is CompleteVirtualPostfixIspMailSetup. Enjoy it once you have finished this basic howto.

System Overview

In our setup, Postfix sends & retrieves mail from Internet and stores in the user mail boxes while clients in the Internet can retrieve their mails either from Courier IMAP or POP3. The user authentication is done by Courier Authdaemon. The following diagram shows this process.

attachment:PostfixSetupOverview.jpg

Install Postfix

In this setup I assume that your domain is yourdomain.com and it has a valid MX record call mail.yourdomain.com. Remember to replace yourdomain.com with your actual domain in the example codes in this howto. Also I assume that you know what an MX record is. To find out MX your type in a terminal:

dig mx yourdomain.com

To install postfix

sudo apt-get install postfix

Intall mailx package for use as command mail utility program. Mail command is installed with this package.

sudo apt-get install mailx

Test your default setup

Add a user before you start this.

sudo useradd -m -s /bin/bash fmaster
sudo passwd fmaster

Test your default installation using the following code segment.

telnet localhost 25

Postfix will prompt like following in the terminal so that you can use to type SMTP commands.

Trying 127.0.0.1...
Connected to mail.fossedu.org.
Escape character is '^]'.
220 localhost.localdomain ESMTP Postfix (Ubuntu)

Type the following code segment in Postfix's prompt.

ehlo localhost
mail from: root@localhost
rcpt to: fmaster@localhost
data
Subjet: My first mail on Postfix
Hi,
Are you there?
regards,
Admin
. (Type the .[dot] in a new Line and press Enter )
quit 

Check the mailbox of fmaster

su - fmaster
mail

When your type mail command an output like follows display in your terminal.

Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/fmaster": 2 messages 2 new
>N  1 root@localhost     Mon Mar  6 12:49   13/479   Just a test
 N  2 root@localhost     Mon Mar  6 12:51   15/487   My first mail
&

You will observe that mails are indexed by numbers and you can type the number of which the mail that you want to read. For example type no 2 to read the 2nd mail. The type q}} to quit. The mail will be written to a file called {{{mbox}} in user's home directory. According to our example {{{/home/fmaster/mbox.

All messages in an mbox type of mailbox are concatenated and stored in a single file. The beginning of each message is indicated by a line whose first five characters are "From " and a blank line is appended to the end of each message

Setting Postfix Support for Maildir-style Mailboxes

Maildir is a format for an e-mail spool that does not require file locking to maintain message integrity because the messages are kept in separate files with unique names. A Maildir is a directory (often named Maildir) with three subdirectories named tmp, new, and cur. The subdirectories should all reside on the same filesystem.

Another reason to use Maildir format is that Courier IMAP/POP3 servers only work with Maildir format of mailboxes.

Please find out more about Maildir [http://en.wikipedia.org/wiki/Maildir here]

 sudo  vi /etc/postfix/main.cf

Add the following code segment:

home_mailbox = Maildir/

Comment the Line  mailbox_command = procmail -a "$EXTENSION" adding a "#" at the beginning

Restart Postfix to make changes effect.

sudo  /etc/init.d/postfix restart

Test your setup again

Installing courier IMAP and POP3

sudo apt-get install courier-pop
sudo apt-get install courier-pop-ssl 
sudo apt-get install courier-imap
sudo apt-get install courier-imap-ssl 

= Adding local domains to postfix

sudo   vi /etc/postfix/main.cf

Add your domain to:

sudo vi /etc/postfix/main.cf

Add your domain to mydestination. Once added it should be like the following code segment.

...
mydestination = mail.fossedu.org, localhost.localdomain, localhost, yourdoamin.com
...

Add your local network to:

sudo vi /etc/postfix/main.cf

I assume that your local network is 192.168.1.0/24 and add your local network to mynetworks. Once added it should be like the following code segment.

mynetworks = 127.0.0.0/8, 192.168.1.0/24

Make Postfix to receive mail from the Internet

Set inet_interfaces = all in /etc/postfix/main.cf using:

sudo vi /etc/postfix/main.cf

Finally Restart Postfix;

sudo  /etc/init.d/postfix restart

Test your setup again using following code:

telnet mail.yourdomain.com 25
ehlo yourdmain.com
mail from: root@yourdomain.com
rcpt to: fmaster@yourdomain.com
data
Subject: My first mail for my domain
Hi,
Are you there?
regards,
Admin
. (and Enter In a new Line)
quit 

Check the mailbox of fmaster

su - fmaster
cd Maildir/new
ls

Now you will see mail has a separate file

Testing Courier POP3

Type in a terminal:

telnet mail.yourdomain.com 110

Use the following example code segment for your test. Be intelligent to tweak the changes appropriately to your environment.

Connected to mail.yourdomain.com (69.60.109.217).
Escape character is '^]'.
+OK Hello there.
user fmaster
+OK Password required.
pass password
+OK logged in.
quit

Testing Courier IMAP

Type in a terminal:

telnet mail.yourdomain.com 143

Use the following example code segment for your test. Be intelligent to tweak the changes appropriately to your environment.

* OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS XCOURIEROUTBOX=INBOX.Outbox] Courier-IMAP ready. Copyright 1998-2005 Double Precision, Inc.  See COPYING for distribution information.
a login fmaster password
a OK LOGIN Ok.
a logout

Adding TLS (Transport Layer Security)

Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet. Using this we tell Postfix to authenticate when they are sending mail. This will provide a way to secure our mails and stop un-authorized relaying etc.

Please find out more about TLS [http://en.wikipedia.org/wiki/Transport_Layer_Security here]

To add TLS support for postfix:

sudo  apt-get install postfix-tls

Howto created by: ChinthakaDeshapriya.

CategoryDocumentation