Citadel offers and easy to install and easy to configure mail server.

On an Ubuntu server you can install the suite with:

sudo apt-get install citadel-suite

During the install you will be asked several questions.   The first question you will be asked if you want to use Apache for the web interface or WebCit.  This example shows the choice of WebCit which is the easiest option.

You will need to select a port that the server will run on so you can connect to the web interface.  You can choose any port over 1024.

Once installed you can access your server at the port that you entered.  Usernames and passwords will be collected from /etc/passwd or LDAP.