The e-mail I receive doesn't contain all the form data, some information is missing

You probably have the wrong enctype parameter set in your <form> tag.

Open your form in a plain text editor (like Wordpad or Notepad on Windows) and find the line that begins with <form. If this line contains a parameter named enctype="text/plain" delete it.

Example of a WRONG form tag:

<form method="post" action="https://www.formnut.com/process.php?id=XXXX&formid=YYYY" enctype="text/plain">

Example of a CORRECT form tag:

<form method="post" action="https://www.formnut.com/process.php?id=XXXX&formid=YYYY">