The bits are free. The downtime is not.
In the ecosystem of Microsoft enterprise software, few rituals inspire as much respect, dread, and meticulous planning as downloading a Cumulative Update (CU) for Exchange Server 2019. At first glance, it seems simple: navigate to the Microsoft Download Center, click a link, and retrieve a multi-gigabyte .ISO or .EXE file. But any Exchange administrator knows that the act of downloading the CU is the least significant part of the process . exchange 2019 cu download