Be default, intranet users are authenticated using the password stored by the
MySQL database. Intranet user accounts can also authenticated via POP/IMAP. This does require that PHP has the ldap
extension compiled or enabled. Requires php IMAP support.
The administrative user has access to a link called Intranet Administration. Click on this.
Click on User accounts.
Click on the user edit icon 
beside the user account you want to
modify.
Change authentication method to Email.
Below this enter the email login username.
Examples:
fred.frog
IMAP settings
Edit the Intranet config file includes/config.php
Set a value for the $MAILSERVER parameter. This requires information about the server ip and protocol port number.
Used for authenticating users via imap/pop3. Check php website for information on syntax. http://www.php.net/manual/en/function.imap-open.php
Examples:
$MAILSERVER = "{hostname:143/imap}";
$MAILSERVER = "{hostname:110/pop3}";