JSFiddle - React, Tailwind, and code Playground

HTML

<form id="test2">
<p class="c">
<label>Entrez une adresse e-mail du <a href="http://groland.com">Groland</a> (.grd)<br />
please enter an e-mail address with .grd TLD<br />
<input  id="test3" type="email" required="required" /></label>
<button type="reset">Effacer</button>
<button type="submit">Valider</button>
</p>
</form>

JavaScript

window.addEventListener('load',function()
{
  var ceinput = document.getElementById('test3');

  ceinput.addEventListener('input',function(e)
    {
      this.setCustomValidity('');
      if (this.validity.valid && !/\.grd$/.test(this.value))
      {
        this.setCustomValidity('Groland Telecom ne permet d\'utiliser que les adresses e-mails du Groland.');
      }
    },false);
    
},false);