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Exchange 2016 – Active Directory Forest Functional Levels

One of the minimum requirements for Exchange 2016 installation is active directory forest function level which should be 2008 or later.

For two cases you may receive error that the function level should be upgraded to windows server 2008 R2 or later.

The first case is when install exchange server 2016 while you are having domain controller which is installed on windows server 2016.

The second case is when you need to install exchange server 2016 with cumulative update 7 or later.

But the difference is the error on the 1st case will not block the installation while on the second case you will not able to install the exchange server 2016.

The error should be as following:

To solve this issue you should raise the active directory forest function level as following steps:

  • Check properly your domain with this command-line(PowerShell)

Import-Module ActiveDirectory


You can see your correct ForestMode (maybe windows2003Forest)

  • Raise now your Forest Functional Level (Run your PowerShell as Administrator)

Set-ADForestMode –Identity NAMEofTheforest.local -ForestMode Windows2008R2Forest

Ratish Nair

Microsoft MVP | Office Servers and Services

Team @MSExchangeGuru

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