Contacts are entries in your Outlook contacts folders Anything else isn't a contact, as far as Outlook is concerned.
Exchange uses Active Directory to manage its address lists, which users access either through the Exchange service or, if they're connecting to Exchange by POP/IMAP, via LDAP, if the server supports it.

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Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
>I have noticed that when I add a member from our directory service
> (ldap) to a distribution list, it is not considered a "contact". What
[quoted text clipped - 5 lines]
> exchange server address book, if I add a member from that address book
> to a distribution list in outlook, is it a contact?
calxn - 03 Jun 2005 22:42 GMT
Ok, but if I add a member from that I look up (via the outlook address
book) on an LDAP source to a distribution list, why is that new
addition not considered a "contact?"
I am asking this because I am writing software to retrieve members from
a distribution list. At first, it was confusing until I saw there was
a difference between a personal address book contact and a contact you
pulled from an ldap source.
Sue Mosher [MVP-Outlook] - 04 Jun 2005 00:09 GMT
It's not a contact, because it is not stored in an Outlook contacts folder. It's stored in the LDAP directory.

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Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> Ok, but if I add a member from that I look up (via the outlook address
> book) on an LDAP source to a distribution list, why is that new
[quoted text clipped - 4 lines]
> a difference between a personal address book contact and a contact you
> pulled from an ldap source.