OAB Diagnostics Logging

The following entry shows up in the Event Log on a regular basis, but it doesn't reveal much info:

Log Name:      Application
Source:        MSExchangeSA
Date:          13-4-2010 5:07:39
Event ID:      9327
Task Category: (13)
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      MAIL-MBX1.Inframan.local
Description:
OALGen skipped some entries in the offline address list '\Global Address List'.  To see which entries are affected, event logging for the OAL Generator must be set to at least medium.
– \Default Offline Address List

The first thing we have to do is increase the level of logging: open Exchange Management Console, navigate to Server Configuration and select the appropriate Mailbox Server. In the Actions Pane select "Manage Diagnostics Logging Properties".
In the "Manage Diagnostics Logging Properties" window expand MSExchangeSA and select "OAL Generator". Set the logging level at least to Medium. Click Configure to continue.

After rebuilding the Offline Address Book more detailed information is visible in the Event Log:

Log Name:      Application
Source:        MSExchangeSA
Date:          13-4-2010 10:48:23
Event ID:      9325
Task Category: (13)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      MAIL-MBX1.inframan.local
Description:
OABGen will skip user entry 'John Doe' in address list '\Global Address List' because the SMTP address '' is invalid.
– \Default Offline Address List

Troubleshooting this issue revealed that this particular user is not mailbox enabled, but it has the "ShowInAddressBook" property populated. Therefore, the OABGEN process tries to process this particular user.
This property is populated because the Exchange admninistrator used another mailbox enabled user as a template when creating a new user. During this process the ShowInAddressBook property is not cleared.

Mail-enable this user and Mail-disable this user and all properties are cleared. The issue now no longer appears in the EventLog.

Do not forget to lower the diagnostics logging or your Event Log will fill up rapidly!

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