The Cumulative Update 5 package can be used to run a new installation of Exchange Server 2016 or to upgrade an existing Exchange Server 2016 installation to Cumulative Update 5.
It’s not necessary to install any Exchange Server 2016 cumulative updates or service packs that were released before Cumulative Update 5 before you install this update.
Upgrading and running Microsoft Exchange 2016 w/ Cumulative Update 5 (CU5) discontinues the functionality of individual mailbox or mail item restores. This change in the Exchange platform is known to effect multiple backup products including Kroll OnTrack (Also white labelled as NetApp’s Single Mailbox Recovery (SMBR)single, Veritas Backup Exec, and Veeam Backup & Replication.
There is currently no path to roll back to CU4 from CU5, and no ETA on a resolution. It is possible that Microsoft may re-release CU5 or offer a fix within CU6.
In the absence of a fix or workaround, it is recommended to ensure proper quotas are defined within Exchange with regards to Deleted Items Retention. It should also be a reminder to confirm healthy and successful backups are in place.
Here are the vendor released KB articles:
Kroll Ontrack PowerControls for Exchange cannot open database on Exchange 2016 CU5
“You may want to hold off upgrading to the recently released Cumulative Update 5 (KB4012106) if mailbox item-level recovery is important for you. A couple of customers who already upgraded reported us restore failures in Veeam Explorer for Exchange, and after researching those we have found the cause being the significant change in one mailbox database structure. We’re now updating Veeam Explorer for Exchange to be able to parse the new blob format correctly, and are planning to include the fix in Veeam Backup & Replication 9.5 Update 2 – which we’ll be delaying for about a week over this and a few other last minute issues.”
I am getting issues with CU5 and SMBR 7.2.1 SMBR mounts the source databse file but has a function call failure when you try to do anything with an account. I have checked the DB files in stellar phoenix mailbox exchange recovery and can see all the folders and mails so the file looks fine is just SMBR cannot read it.
Stellar Phoenix Exchange Recovery is a different type of product. The results their are not indicitive of the health of a database, but what it can do in a recovery situation. That may be a good solution for you, but I suggest opening a ticket for support of the SMBR error to find out what the cause may be.