PMDF can use LDAP in many ways to build and maintain a large-scale
secure mail environment. PMDF allows you to leverage your existing
LDAP database to simplify mail administration and authenticate users'
e-mail access. In addition, mail administrators can use the LDAP v2
or v3 compliant LDAP server of their choice, because PMDF is not tied
to any particular LDAP vendor's solution.
A messaging backbone is responsible for receiving, storing, routing,
and delivering messages within an enterprise or to remote sites via
PMDF, a full function SMTP server that implements ESMTP, can be used
either in conjunction with a firewall or can be used on the firewall
itself to dramatically improve the functionality and performance of
a firewall for messaging.
The Cost of Migrating From Microsoft Exchange v5.5 to v2000. A White
Paper by Ferris Research April 2002