The HTML5 shiv for older browsers was needed in 2015 when that tutorial was posted. You can safely remove it if you want to. The form processing script works fine without it.
Thank you for sharing this! I barely understand it, but I get the gist. Since I've created my own form on my html web page, can I add all this code to the page to make it work? I really don't know what I'm doing.... Thanks in advance for your reply.
Please do not post a query with the same substance in different places, this will contribute to confusing answers, especially because you are a newbie to code.
For others, following this post, please answer the other post at https://community.adobe.com/t5/dreamweaver/code-for-submitting-a-simple-contact-form-to-my-email/m-p...
Ask your hosting provider if your plan supports PHP and the PHP mail () function?
If not, you'll need to find another solution like this mail sending library on GitHub which supports SMTP authentication and a lot more.
Creating secure contact forms and processing scripts are no trivial matter. What you don't know can hurt you and your site. When in doubt, don't risk it. Use a 3rd party form service like Wufoo.com or Jotform.