Step 1: Identify the mailbox database hosting organization mailbox with OAB Gen capability.Use the following command to list the arbitration mailboxes with persisted capability of OABGen and database on which this mailbox is hosted: The server that where the database is MOUNTED, is the OAB generation server. For kicks, I created a new standalone database on one of new server, and moved OAB system mailbox over with New-Moverequest cmdlet.
If Outlook is left running constantly in Cached Exchange Mode, it updates the Offline Address Book automatically about once a day, depending on Address Book updates on the server running Exchange.Move was successful, however, the uninstall failed again with same exact error.Solution While I can always remove MBX1 manually by deleting it from ADSIEDIT, to take the easy way out, but I decide to check one more place in AD, the properties of each Office Address Book object. After i manually changed it to MBX3, issue was resolved.I removed database copies off old mailbox servers MBX1 and MBX2, and made sure they are not owning any databases.I then evicted them out of existing DAG, so Exchange 2013 binaries can be uninstalled properly. MBX1 was throwing a fit during pre-requisite check with following error message. In Exchange 2013, Offline address book is now generated by a system mailbox. First, i need to identify OAB generation server in a DAG environment.