Email marketing with information via post?

I know it seems impossible, but a leader here of the company, had the idea of putting an email marketing already with information that will facilitate the registration here for the training.

She had originally given the idea of sending the link to the training registration with the training registration code via URL, so that I could get it via GET when loading the page. But she gave a preference that by clicking on the make button, I could get it via POST?

Is there any way to do this?

So in this email marketing, you would have to have a way to send one

<form method='post' name='frmCodPromocional'>
   <input type='hidden' value='cod_promocao'> 
   <input type='submit' name='btnEnviar'>
</form>

Where cod_promocao would be the code I would send?