I have posted the ISO for the interim release dubbed "WGS" (for Workgroup Server).
This version has SAMBA +OpenLDAP (+ WWW) like all of the previous releases, but it also includes DHCP Server, DNS Server (w/Dynamic updates from DHCP), IMAP/POP3/SMTP servers.
I have configured the mail servers to authenticate from the OpenLDAP database using the existing Samba information. This means that if you have added a user for Samba, you have added a user for email without any further configuraton.
Please use the Web GUI for adding users, as I have not updated the command line utility in quite some time.
WebGUI: https://<yourIP>:8443
User Name: admin
Password: <entered during setup>
TODO: I am going to add another default group to the system called "Email Users" and re-write the LDAP auth for the mail servers to require that group so that you have an option of if a user has email rights on the server or not.