With the introduction of Exchange 2007 we now have the ability to create a Web-distributed version of the OAB (OAB Version 4). Offline Address Books are distributed by CAS server via dedicated OAB virtual directory.
When first Exchange 2007 Client Access Server is installed in the organization, it's OAB virtual directory becomes associated with default Offline Address Book. File Distribution Service running on Client Access Server will periodically synchronize Offline Address Book virtual directory data with data generated by OABGen server.
To load balance default OAB or start distributing other OABs in the org, additional Virtual Directories can be added for load balancing. This will allow the Offline Address Book to be copied from the OAB Generation Server to the Client Access Server via the Microsoft FDS Service.
In certain scenarios it is possible for the OAB generation and Client Access Servers to reside in different child domains. The File Distribution service builds an UNC path to the Offline Address Book using short server name. If we are unable to resolve the NETBios name of the server you might see an event like the one listed below:
Event Type: Warning
Event Source: MSExchangeFDS
Event Category: General
Event ID: 1018
Description: Process MSExchangeFDS.exe (PID=3420). Failed to connect to remote server MCHH235E. The remote server may be down, or its Server service may not be running.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
The MSExchangeFDS service will try to contact the OAB generating server 5 times and if it fails it will then log an error telling you that it will now give up contacting the OAB generating server. This behavior is by design.
How to Fix
Once you enable DNS short name resolution the Offline Address Book will get replicated successfully to the distribution point on the Client Access Server.
Thanks to Vladimir Kritchko for reviewing this blog.
NOTE: The information below is now part of the Exchange 2007 official documentation. You can find the official version here:
http://go.microsoft.com/fwlink/?LinkId=122545 - Error 1018 Received When Web-based Distribution OABs Fail to Replicate