Form Post From Email

We have created a new ASP file that will process a standard HTML form, write the data submitted in the form to a database table, and send us an email of the data submitted. All works OK except if we now send that form code as part of an email, the form appears OK at the receiver's end, but when you fill in the form, there is no data that is transmitted back to the asp file.

The ASP file acknowledges the receipt of the form, and all that, but there is no data in the email and no data in the table.

It is obviously something that is happening when it is sent as an email, but I have seen this sort of thing done before, with a form in an email, and I wonder if anyone has some clues as to what we need to do to make the form work properly when sent as an HTML email.