By default, Exchange 2010 creates undeliverable messages (NDR) in the language of the sending system. Unfortunately, this does not always work reliably, at least not for NDRs that leave the organization. This can be remedied by setting a fixed language for external NDR messages:
Set-TransportConfig -ExternalDsnDefaultLanguage en-us -ExternalDsnLanguageDetectionEnabled $false
This command switches off the automatic detection of the language for the NDRs and sets the language to English (US). If you also want to set the language for internal NDRs, you can use this command:
Set-TransportConfig -InternalDsnDefaultLanguage en-us -InternalDsnLanguageDetectionEnabled $false
After executing both commands, both internal and external NDR messages are in English.
