Additional standards have been embraced, making Exchange easier to integrate into corporate environments. This makes sense, since Exchange 2000 doesn't use its previous directory services, but instead is integrated into the Active Directory of the domain. Security and distribution lists are part of the Windows 2000 AD that E2K uses. This native use of Windows 2000 security makes E2K both secure and easier to administer. Addressing via the AD can slow messages down, so Microsoft has implemented a Directory Services Access API that caches addresses.
Any address held in the cache is maintained for two hours.
The DS Access API uses LDAP and connects to domain Global Catalogs. DS Access will use a GC for nine hours and then randomly switch to another GC on its list. There can be up to 10 GCs within a domain that are on this list and that the DS Access will cycle between. Microsoft has said that future plans will include accessing these GCs via SSL for wide Internet deployment. Users will probably notice the addition of unified messaging the most.