Event ID - 9127

Event Id9127
DescriptionOALGen encountered error [0x%1] while calculating the OALs.
Event InformationExplanation :
This event indicates that the System Attendant was unable to generate the Offline Address List.

This issue can occur if the Offline Address Book (OAB) does not have a replica on any Public Folder Store. By default, the OAB replicates its contents to the public folder store of the server on which it is installed. If the public folder store is removed from the replication configuration of the OAB, then the 9127 error can occur. 
Offline Address List Folder may not be present. 
Check if the OAL folder has the appropriate proxy addresses stamped on it. If not, check to see that the Recipient Update Service is working correctly. 

User Action :
Ensure that the Offline Address Book System Folder has been created. 
If the OAB is present, then ensure that it has an SMTP Address stamped on it. This is done by the Recipient Update Service for the Domain. 
Check to see that the OAB is replicated to at least one Public Folder Store.
Reference Links Offline Address List is empty and Event ID 9127 is logged in the application event log in Exchange 2000 Server

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