We'd like to seek your assistance regarding on the NDR message. One user try to send an email to our domain and he get's an error below.
Delivery has failed to these recipients or distribution lists:
The e-mail system had a problem processing this message. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.
Diagnostic information for administrators:
Generating server: xxxxxx.xxxxxx.com.ph
#< #5.6.0 smtp;550 5.6.0 CAT.InvalidContent.Exception: ExchangeDataException, invalid message class; cannot handle content of message with InternalId 6136496, InternetMessageId <BCBB5E7F065247478D6845A9D90FF76567A3DD5CD2@email@example.com>.> #SMTP#