This event indicates that Microsoft Exchange File Distribution service did not find an offline address book (OAB) file.

• If MSExchangeFDS event 1021 is logged, the ExchangeOAB directory could not be found on the Exchange server. This is typical if Oabgen.dll (referred to as OABGen) has never been run on this server. The Microsoft Exchange File Distribution service (MSExchangeFDS) connects to the ExchangeOAB directory for offline address book (OAB) files so that these files can be distributed to Outlook clients. If MSExchangeFDS cannot find the ExchangeOAB directory, OAB distribution to Outlook clients may not work. This event may also occur if MSExchangeFDS does not have the necessary permissions to access the ExchangeOAB directory.
  
  
• If MSExchangeFDS event 1022 is logged, the Microsoft Exchange File Distribution service did not find an OAB manifest file (oab.xml). The File Distribution service requires this file to synchronize OAB files between Exchange servers that have the Mailbox server role and Client Access server role installed.
  
  This event may occur if either of the following conditions is true:
  
  
  • The OAB manifest file (oab.xml) has not been generated yet. This file is generated when the corresponding OAB is updated. By default, every OAB is updated daily at 5:00 A.M.
    
    
  • The Exchange Servers group does not have the Read permission on this manifest file (oab.xml).
    
    

  Note:
  If the corresponding OAB update has yet to run, you may ignore this event. Otherwise, see the "User Action" section in this topic.

  Note:
  The OAB GUID that follows the ExchangeOAB file share in the event description indicates the corresponding OAB.

To resolve this warning, do one of the following:

• If MSExchangeFDS event 1021 is logged, open the directory in which Exchange has been installed on the Exchange server that logged this event. For example, open C:\Program Files\Microsoft\Exchange Server. Then, verify that the ExchangeOAB directory exists. If it does not exist, run the following Exchange Management Shell command:
  
  Update-OfflineAddressBook "Default Offline Address List"
  
  If the ExchangeOAB directory exists, make sure that it is shared and that the Exchange Servers group has the Read permission assigned. For more information, see Update the Offline Address Book.
  
  
• If MSExchangeFDS event 1022 is logged, make sure that Exchange Servers group has the Read permission on the oab.xml file that is specified in the event description. Then, regenerate the manifest file by following these steps:
  
  
  1. Note the OAB GUID that follows the ExchangeOAB file share in the event description.
     
     
  2. Run the following Exchange Management Shell command:
     
     Update-OfflineAddressBook -Identity <offline address book identifier>
     
     

  Note:
  In this command, replace <offline address book identifier> with the GUID that you determined in the previous step.

  1. Restart the Microsoft Exchange File Distribution service from the Microsoft Windows Services console on the Exchange server that logged this event.
     
     

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.