Default offline address book not updating exchange 2016
I solved this problem by including a detailed planning phase in the guide that leads you through the process of discovering all of the most important details of your environment that have an impact on the migration.
If you open the Outlook Address Book and do not see the name or e-mail address you are looking for, you might need to choose another address book from the Address Book list.
If your company has a Global Address List (GAL), you also see it in the Address Book list.
Written by Support Info Bridge Overview: When you don't see all users in the Offline Address Book (OAB), then you might need to make some changes in the Offline Address Book.
Exchange 20, the oab generator is performed by system mailbox.
"One of these persisted capabilities is called Organization Capability OABGen and it is this persisted capability that controls whether this arbitration mailbox can generate an OAB.