A general purpose LDAP solution?

[Jon Theil Nielsen]

Hi list!

I have speculated a lot about implementation of (Open)LDAP on my
sever. By I haven't yet found the right (and logical) way to do it.
I'm running FreeBSD 7.0-Release with some different server applications
- Samba PDC
- Virtual mail server (Postfix, MySQL, Courier-IMAP)
- VPN (currently with mpd4)
- Apache-2.2.8 web server (with PHP and MySQL)
I would like to implement LDAP for:
- authentication of UNIX/login users
- authentication of Samba users
- authentication/authorization of virtual mail users
For the first part, I got useful information from a previsous thread
(http://unix.derkeiler.com/Mailing-Lists/FreeBSD/questions/2008-02/msg01047.html)
and for the second part, i guess there is sufficient howtos to make it
work.
My biggest question right now is if is possible to combine all three
things in one data structure. And which in which order I should make
the different implimentions.
Excuse my total lack of understanding, but is it possible to have a
structure with a superior unit such as OU=<some organization> which
could contain several virtual domains and the actual doamin for my
PDC?

-- 
Jon Theil Nielsen