AD002

AD Forest Function Level

Check to make sure that the AD Forest is at the correct level.

Best Practice

Exchange Server 2013 requires, at a minimum, Windows 2003 functional level for the Active Directory Forest Levels. Exchange Server 2016 requires, at a minimum, Windows 2008 functional level for the Active Directory Forest Levels.

What To Do

If you are installing Exchange Server 2013, make sure to upgrade your forest levels to Windows 2003 functional levels.
If you are installing Exchange Server 2016, make sure to upgrade your forest levels to Windows 2008 functional levels.

References

https://msdn.microsoft.com/en-us/library/cc730985.aspx

Exceptions