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Change in Microsoft Exchange 2016 Cumulative Update 5 (CU5) Removes The Ability to Perform Individual Mailbox or Mail Item Restores

Will Fulmer - Chief Engineering Officerby William Fulmer, Chief Engineering Officer

Cumulative Update 5 (CU5) for Microsoft Exchange Server 2016 was released on March 21, 2017.


  • 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.

Please let us know if Helient can be of assistance in supporting your Microsoft Exchange environment. Contact us at

Here are the vendor released KB articles:

Kroll Ontrack PowerControls for Exchange cannot open database on Exchange 2016 CU5

Veritas Backup Exec – Exchange 2016 CU5 Support

After installing CU5 for Exchange 2016, Backup Exec 16 will not show GRT items during restore

Published in the recent Veeam Digest

“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.”

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