Dealing with contact forms on self hosted websites isn’t easy:
they require a dynamic server side response.
RealSender simplifies it through “sending via html form” features.
they’re often abused by robots that automatically fill them to send spam.
The simplest and most widespread solution is to add the “Google’s reCAPTCHA v2 form validation”.
without some styling and positioning, forms just look awful.
A well written article that helps styling them: 10 CSS HTML Form Designs.
This is the path that I’ve followed.
The third step has just been completed.
Now it all seems simple.