Hello,
You can simply consider adding the .customjs Class on the .form-widget Element to disable the Validation JS on the Form. And then use the following Input code inside the Form:
<input type="email" id="template-contactform-email" name="template-contactform-email" value="" class="required email sm-form-control" required>
You will see the exact same result with the Default HTML5 Check and with the Canvas's Validation Plugin turned off. The user@website will get passed.
Hope this Helps!
Let us know if we can help you with anything else or if you find any further issues.