“This mailbox server is responsible for generating an offline address book”
I was trying to uninstall Microsoft Exchange 2013 after moving to Exchange 2016 but kept getting the error “This mailbox server is responsible for generating an offline address book” in the Readiness checks.
I ran ‘Get-Mailbox – Arbitration’ to verify all the mailboxes had been moved.
Nothing appeared to be pointing at the old server and I could not find any mailboxes on the server.
In the end I ran ADSIEdit and found under Configuration > services> Microsoft Exchange > First Organisation> Address List Container > Offline Address Lists that the Offline Address Book had a reference to the old server.
If you go to the properties of the Offline Address List and scroll down to the offLineABServer entry and check the name of the server – update this to your new server.
Now rerun your Exchange Uninstall Readiness checks and you should be able to remove Exchange 2013 from your environment.
You may need to check other address books in ADSIEDIT but this worked for me.
Please let me know in the comments if it helped you and if you there was anything else you need to do.