OBM Mail is based on cyrus, postfix and some automation done in perl.
OBM LDAP is the LDAP directory managed by OBM and synchronized with the OBM database.
OBM Sync is the OBM synchronisation server that support Thunderbird, Outlook and PDA.
Roundcube is the preferred webmail for OBM. The OBM connector for roundcube brings bi-directional contacts synchronization.