A product key tells Exchange Server 2016 or Exchange Server 2019 that you’ve purchased a Standard or Enterprise Edition license. If the product key you purchased is for an Enterprise Edition license, it lets you mount more than five databases per server in addition to everything that’s available with a Standard Edition license. If you want to read more about Exchange licensing, see Exchange Server editions and versions.
Your server is automatically licensed as a trial edition if you don’t enter a product key. The trial edition functions just like an Exchange Standard Edition server and is helpful if you want to try out Exchange before buying it or running lab tests. The only difference is that you can only use an Exchange server licensed as a trial edition for up to 180 days. If you want to keep using the server for more than 180 days, you’ll need to enter a product key, or the Exchange admin center (EAC) will start to show reminders that you need to enter a product key to license the server.
If you have installed Exchange Server and it is ready, you only need the Active Exchange Server Key. Please refer to the guide below:
If you have not installed Exchange Server and need guidance on step-by-step installation in Windows Server. Please refer to the guide below:
1. Download Exchange Server build numbers and release dates
Exchange Server 2016:
https://learn.microsoft.com/en-us/exchange/new-features/build-numbers-and-release-dates?view=exchserver-2016#exchange-server-2016
Exchange Server 2019:
https://learn.microsoft.com/en-us/exchange/new-features/build-numbers-and-release-dates?view=exchserver-2016#exchange-server-2019
2. How to install Exchange Server
Exchange Server 2016:
https://www.starwindsoftware.com/blog/installing-exchange-server-2016-on-windows-server-2016
Exchange Server 2019:
https://www.stellarinfo.com/article/setup-new-exchange-server-2019.php