The administration and maintenance of Microsoft Exchange Server to ensure secure, reliable, and efficient email and collaboration services across an organization.
Hi @Caspar ,
Exchange 2016 will keep functioning, the only thing that will happen is there will be a reminder in EAC to enter a licence key. I believe you will be required to get an Exchange 2016 product key first yes, as you cannot upgrade an evaluation of Exchange 2016 to Exchange 2019.
For more information on entering your Exchange server product key, see:
Enter your Exchange Server product key
https://learn.microsoft.com/en-us/Exchange/plan-and-deploy/post-installation-tasks/enter-product-key?redirectedfrom=MSDN&view=exchserver-2016
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Best regards,
Leon