Cumulative Update 5 (CU5) for Exchange Server 2013 will be released soon TM , but before that happens, I wanted to make you aware of a behavior change in the Offline Address Book that is shipping in ...
Updated Jul 01, 2019
Version 2.0
Blog Post
@Jeff - If by OAB arbitration mailbox, you mean the SystemMailbox, then no, you don't have to configure anything. CU5 will link all OABs to the SystemMailbox. If you have other OAB generation mailboxes in the environment, you will have to configure them
manually after CU5 is deployed.
Prior to CU5, all OABs are generated in each OAB generation mailbox, so if in your scenario, all the OABs are generated by the SystemMailbox, then after you install CU5, all OABs will be continued to be generated by that mailbox, and thus no full download will
occur. If on the other hand, you have multiple OAB generation mailboxes in a site today, (see the 2nd deficiency), your users already having multiple full downloads today, so when CU5 is deployed on those servers, they will experience another full download
(as they will now be pointed to the SystemMailbox).