Introduction

In this setup you will be running a small to medium sized email server with Postfix virtual mailboxes for Separate domains and non-Linux Accounts. I do not intend teach you basic stuff with Postfix here. If you are new to Postfix please work on my PostfixBasicSetupHowto to understand basics and proceed with this howto. Also I will tell you howto integrate with ClamSMTP, an SMTP filter for Postfix and other mail servers that checks for viruses using the ClamAV anti-virus software. It aims to be lightweight, reliable, and simple and easy to configure

Example Setup

In this howto I assume that your are going to host mails for two example domains. Namely domain1.com and domain2.com. Be ready to replace these with your actual domains.

Install Postfix

To install postfix

sudo apt-get install postfix

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

sudo apt-get install mailx

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.

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/

Remove the Line  mailbox_command = procmail -a "$EXTENSION". We are not going to use it.

Restart Postfix to make changes effect.

sudo  /etc/init.d/postfix restart

Postfix virtual Mailboxes for Separate Domains and Non-Linux Accounts

As a system hosts more and more domains and users, it becomes less desirable to give every user their own Linux system account.

With the Postfix virtual mailbox delivery agent, every recipient address can have its own virtual mailbox. Unlike virtual alias domains, virtual mailbox domains do not need the translation from each recipient addresses into a different address, and owners of a virtual mailbox address do not need to have a Linux system account.

The Postfix virtual mailbox delivery agent looks up the user mailbox pathname, uid and gid via separate tables that are searched with the recipient's mail address. Maildir style delivery is turned on by terminating the mailbox pathname with "/".

Look at the following figure and it is our directory structure for mailboxes.

attachment:VhostsDomains.png

I suggest you to transfer all domains into virtual mailboxes. Even if you have setup postfix with one domain , we will make that domain a vrtual domain. Acculally you do not need to do this ,but doing this way you will have well organized mail system , and no need to avoid this. Having Postfix host one real domain and the rest virtual means that you will always need to configure Postfix twice: once for each type of domain.

To do that, let's change our myhostname line in main.cf to read:

myhostname = localhost

Create Virtual Mailbox Owner

In our setup all virtual mailboxes are owned by a fixed uid and gid 5000. If this is not what you want, specify lookup tables that are searched by the recipient's mail address.

To create virtual mailbox group:

sudo groupadd -g 5000 vmail

To create virtual mailbox owner:

sudo -m -u 5000 -g 5000 -s /bin/bash vmail

Open main.cf

sudo vi /etc/postfix/main.cf

Setup Postfix to Use Virtual Mailboxes

Then add the following code segment to main.cf

virtual_mailbox_domains = /etc/postfix/vhosts
virtual_mailbox_base = /home/vmail
virtual_mailbox_maps = hash:/etc/postfix/vmaps
virtual_minimum_uid = 1000
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
virtual_alias_maps = hash:/etc/postfix/valias

In the first line, we're using a text file called vhosts. You can actually name this anything you want. Inside this text file will be a simple one-column list of all the domains you are hosting. For example, add your all domains there.

sudo vi /etc/postfix/vhosts

Add the the following codes:

domain1.com
domain2.com

This is my exmaple use your own domains here.

The next line virtual_mailbox_base specifies the base directory where we shall store all of our mail. Again, you can choose anything you want. In our case it will be our '''vmail''' owners's home directory /home/vmail

The third line points to a textfile I called '''vmaps'''. This is a two column text file. The first column specifies a virtual email address. The second column specifies that persons mailbox location. Just like with real domain hosting, if you specify a / at the end of the location, it becomes Maildir format. If not, it is mbox. Any way in this howto we use Maildir format.

Setup this file as in this example:

sudo vi /etc/postfix/vmaps

Add the entries like the following codes:

info@domain1.com  domain1.com/info/
sales@domain1.com  domain1.com/sales/
info@domain1.com  domain1.com/info/
sales@domain1.com  domain1.com/sales/

Convert vmaps into a hash file by running:

sudo postmap /etc/postfix/vmaps

Remember to execute the above command every time when you add new map.

Restart Postfix to make changes effect.

sudo  /etc/init.d/postfix restart

My exmaple config look like the following

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu/GNU)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

myhostname = localhost
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = $myhostname
mynetworks = 127.0.0.0/8, 10.0.0.0/24
mailbox_size_limit = 0
home_mailbox = Maildir/
virtual_mailbox_domains = /etc/postfix/vhosts
virtual_mailbox_base = /home/vmail
virtual_mailbox_maps = hash:/etc/postfix/vmaps
virtual_minimum_uid = 1000
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
virtual_alias_maps = hash:/etc/postfix/valias
recipient_delimiter = +
inet_interfaces = all

Test Virtual Mailbox Setup

Remember that the directory structure for a particular user is create when you send he gets his firs mail.

Send a mail for info@domain1.com

In a terminal you can type:

mail info@domain1.com

Check the mailbox

cd /home/vmail/domain1/info/new
ls

You see a mail file there. If so, Cheers!!!, you have done it.

Setup Non-Linux Accounts

Now it's time to work on the non-unix accounts.

There are several popular techniques to do this using services such as OpenLDAP or MySQL and mixing that with Courier IMAP. We won't be using any of those. Instead, we're going to be using something much more simple: plain text files.

In order to do this, we'll be using Dovecot. If you've never heard of it, you will now. Dovecot is extremely lightweight, flexible, and from what the author says, secure.

Remember the following command will install Dovecot but removes Courier IMAP/POP3 which if you have installed already them. Take it easy ,let's continue to install it.

sudo apt-get install dovecot-common dovecot-imapd dovecot-pop3d

Yet another howto by: ChinthakaDeshapriya.