It is vital for administrators to know that . Exchange Server supportability matrix - Microsoft Learn
Microsoft releases "Cumulative Updates" (CUs) that serve as full installation media. For example, you can download the Exchange Server 2019 CU15 ISO (approx. 6.0 GB) directly from the Official Microsoft Download Center . These ISOs can be used to install a new server or update an existing one. Microsoft Exchange Server 2019 Iso Download
Organizations with active licensing agreements must download the full ISO through the Microsoft Volume Licensing Service Center (VLSC) . This is the only source for the non-evaluation, perpetual-license version. It is vital for administrators to know that