This seems to be related to
At least you get feedback it is not accepted. Other vendors accept it but silently do not deliver it, eg Hostgator
Not sure if there is a fix / workaround in the meantime
This seems to be related to
At least you get feedback it is not accepted. Other vendors accept it but silently do not deliver it, eg Hostgator
Not sure if there is a fix / workaround in the meantime