In the contact form ‘Mail to site admin‘ section, you need to add the ‘from email‘ address.
Since you want the message from your users email id, we are using the code of the user email here. The code is something like [email-2].
But in some server, they don’t allow to send emails with ‘from addresses’ that are outside the server domain.
So in such conditions, you need to add your own email address with the same domain extension of your server in the ‘from email’ section.