Email, Virtual Domains Solution

Prefix

Developing a solution for serving multiple domains on a single e-mail server can prove to be a challenge. I hope this can help those of you who are having trouble coming up with a good solution.

When developing a solution for the new services.x2studios.com server I had the following requirements to satisfy:

• Server must be fast and reliable
• User names must be unique to their domain
• POP3 and IMAP
• SMTP users must be authenticated

I almost immediately eliminated send mail from the list of candidate MTA's. The first solution I considered implementing was Virtual Domains and Users w/ Postfix / Courier-IMAP / MySQL. This is a good solution for many users, however I found Postfix to be almost as archaic as sendmail. I had previously used EXIM for my home FreeBSD server and was interested in giving it a try. Minimal research lead me to a site with a solution for Virtual Domains with Exim + Courier-IMAP + MySQL. This is an example that I borrowed a lot from when developing our solution.

Overview

This document describes how to set up Exim and Courier IMAP on a MySQL database in order to handle "virtual domains", which means here accepting mails for several domains which must not be local, but the MX record of the domain points to your server. All informations about the domains and the users are stored in a SQL-database. This article also covers how to enable SMTP authentication, setup and use the X2 mailAdmin PHP control panel and my random bitching.This article does not cover how to set up from scratch any of the above mentioned programs. They should already working, and need only to be adapted for this solution.

Just a side note: usernames are e-mail addresses in this solution (so the user name is joe@domain.com not joe).

Requirements

EXIM and Courier IMAP must be compiled with support for mysql (there are other ways, but I'm not going there)

Preparing the DB

We are now ready to create our database structure. Don't worry about copy-pasting from the web page, I have provided a 'dbdump' file along with the X2 Mail Admin package. (remember however that the defaults for uid and gid in the passwd table must be that of the mail user)

Setting Up Courier IMAP

Starting from a running IMAP-Installation, the authmysql module has to be added to the authmodulelist in the configuration file of authdaemon. Edit authmysqlrc; be sure to set up properly MYSQL_SERVER, MYSQL_USERNAME, MYSQL_PASSWORD andMYSQL_DATABASE. Again don't worry I have provided a configuration file for you in the package. They are authdaemonrc and authmysqlrc; simply copy these files to /usr/local/etc/courier-imap/ (for FreeBSD).

Setting up EXIM

Again, I have provided the configuration files for this. All that needs to be done is to change the authentication so that it uses the mysql-database. If you are overly interested in how this works, take a look at the two above mentioned inspirations I used.

Here is the major difference between my solution and the one from Virtual Domains with Exim + Courier-IMAP + MySQL. I have added SMTP authentication. There are three types of common SMTP authentication, as such the following lines were added to the end of the exim configuration file:

You will want to copy the exim_configuration file to /usr/local/etc/exim/configure (for FreeBSD).

Adding the web control panel

I created a web control panel to allow a typical ISP style experience. It has 3 levels of control:

• Admin of the Admin:
  Allowing the addition and subtraction of domains which are controlled by their postmasters.
• Admin:
  The postmaster of each domain is in control of all users and forwards of that domain.
• User:
  Anyone with an e-mail address can change their password using the 'change password' page.

To install the X2 mailAdmin, simple move (or sym-link) the mailAdmin dir into a path accessible by your php enabled webserevr. Now we have to setup the local directory for the vdomains. This directory should be (unless you want to change all my code) /usr/local/vdomains and you must chown the dir to that of the mail user.

This is important!!! You must use a .htaccess file to control access to the /mailAdmin/admin dir. Do not leave this directory publicly available.

Once the mailAdmin is 'installed', open http://yourdomain.com/mailAdmin/admin. You can then add a domain. This will create a postmaster@domain.com account that will be used to admin the domain. You may also remove domains from this page.

Have fun!