The client does not receive the HTML code that I added in the email

The client does not receive the HTML code that I added in the email

When I customize Email Templates in ZOHO DESK the client does not receive the HTML code that I added in the email. The HTML code in question is an access to a google form that appears perfectly in the edit, as shown in the figure below.

" <iframe src="https://docs.google.com/a/diwait.com/forms/d/e/1FAIpQLSc76xrgMO_olK2EfMM4TTuN4zualEN5bs_nAg09sHH7Usrczw/viewform" height="400" width="500"></iframe> "

Follow the example of how to stay in the email:

Best regards