@garyrussell  I think I can be convinced to accept it but I wanted to mention that I am slightly hesitant having this slightly overloaded functionality of the correlationKey property (If null or matches 'correlationId' use the standard correlationId message property, otherwise use the Message header. 

Would it be cleaner to not even check for the 'correlationId' String? Therefore, only use the the standard correlationId property when the correlationKey property is null (Which is the default).