The Cumulative Update 5for Microsoft Exchange Server 2019 includes an important update to the Exchange Server 2019 Sizing Calculator. Improvements are made to the logic to detect whether a design is bound by mailbox size (capacity) or throughput (IOPs), which affects the maximum number of mailboxes a database will support. Earlier versions of the calculator produced incorrect results in some situations. You’re highly recommended to use calculator version 10.4, included with the Cumulative Update 5 for Exchange Server 2019 release, to size Exchange Server 2019 deployments.
Learn about the terminology that Microsoft uses to describe software updates.