Ok, get this.
I have been assigned to write an html form to be EMAILED to clients so that they can fill it in and submit it FROM THE EMAIL CLIENT! apparently emailin
There are only two possiblities: first one the mail client must have a php runtime environment to run the php script locally, also an embedded mail server - which isnt the case for the most of them. Second one is that your mail client acts like a browser and displays the form (which is located still on the internet) in his mail viewing window (which is perhaps possible but i dont know any common mail client doing this).
So you either submit a link to the form or you construct the mail this way, that there're placeholders to be filled and submitted like a normal mail response.