Symptoms
When you use Offline Address Book (OAB) shadow distribution, the OAB files are downloaded from the OAB generation server if they are at least 24 hours old. However, because Microsoft Outlook clients have a default download period of 24 hours, the downloaded files could be up to 48 hours old.
Microsoft Exchange Server Cumulative Update 13 (CU13) introduces a parameter to make the OAB shadow distribution file age limit configurable. In this manner, the OAB is refreshed by the shadow distribution server more frequently.
After this parameter is added, you can configure the age limit value by running the Set-OrganizationConfig cmdlet and using the -OabShadowDistributionOldestFileAgeLimit parameter. For example, to configure the server to download OAB files that are older than eight hours, run the following cmdlet:
Set-OrganizationConfig -OabShadowDistributionOldestFileAgeLimit 08:00:00
Resolution
To fix this issue, install Cumulative Update 13 or a later cumulative update for Exchange Server 2019.
