If you are using Veeam Backup & Replication to protect a Microsoft Exchange 2016 environment, you should not (yet) apply the Cumulative Update 5 (KB4012106) patch to avoid mailbox item-level recovery issue. In the weekly newsletter, Veeam notes that a couple of customers who already upgraded to CU5 reported some restore failures in Veeam Explorer for Exchange, caused by the significant change in one mailbox database structure.