exchange-logo-isolatedOffline Address Books and their existence when running different versions of Exchange comes up alot. So wanted to post up this great article  that covers off what you need to know.

Before installing your first Exchange 2013 server during a migration project you must first review your offline address book configuration.

The issue, as explained in detail by Exchange MVP Andrew Higginbotham here, and mentioned by Microsoft in the release notes and a subsequent blog post, is that Exchange Server 2013 will create a new default offline address book for the organization.

Any mailbox users who do not have an existing OAB assigned to their mailbox directly, or to the mailbox database that they are located on, will download the entire OAB from the new default OAB that Exchange 2013 creates. In organizations with a large OAB or distributed network environment this is obviously not ideal.

The solution is to review your existing OAB configuration. You can check the OAB configured on mailbox databases with a single PowerShell command.

As you can see only two of the six databases in the Exchange Server Pro organization have an offline address book configured.

To avoid mailbox users on the other four databases re-downloading the entire OAB we can assign an OAB to the databases. Again this can be performed with a single PowerShell command in many cases.

Alternatively you can assign the OAB to a database using the Exchange Management Console by opening the mailbox database properties and selecting the Client Settings tab.

exchange-2010-2013-migration-offline-address-book

This is an important configuration item to review during a migration project and should not be overlooked.

 

Courtesy of Paul Cunningham via practical365.com

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