[exim] Ldap and active directory

Hi,
I am putting together another mail gateway using Exim-4.44+Ldap but this
time I need to sync Ldap with Active Directory (2003) so the Admin
doesn't
have to deal with duplicative user management. However, I have not been
able to
get Samba (3.0+) to work with AD, nor have I seen sufficient
documentation on anything else out there that will sync openldap with
AD. Has anybody
done this? Is there another way to do this with Exim? I know there's
something out there because all of the commercial products advertize
syncing with AD or Edir and they run Linux or BSD.
Thanks,
Craig