If somebody is confused about what we are talking about, as this is quite technical, see
iMessage: Use Phone Number Instead Of Email Address
And as this webpage perfectly states, you have to CHANGE what is the default setting of iphone if you want to be able to answer an incoming imessage in your tesla.
The car seems to only support "send and receive : phone number" and nothing more complex than that, especialy it will NOT handle "receive email & phone".
Anyway, hope this helps someone.
If we had a way to report bugs to tesla this would have been solved a year ago.
As a quickfix, what the car
should do is simply look up in the contacts the "email" it has been receiving, and send the answer back to to phone number associated to the same contact. (Just like a iOS phone does. )