- You have root and child domains in Active Directory.
- You have Exchange Server 2016 installed in the root domain.
In this scenario, when a user in a child domain logs into Outlook Web App (OWA) and tries to change language by selecting Settings > Options > General > Region and time zone > Language, and then selects the check box next to Rename the default folders so their names match the specified language, the language can't be changed, and the default folder names mismatch the specified language.