Regular Expression to Validate Case-Sensitive Email Address.

<script type = "text/javascript" language = "javascript">
function validateCaseSensitiveEmail(obj) 
{ 
  var reg = /^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/;

  if (reg.test(obj))
  {
     return true; 
  }
  else
  {
     return false;
  } 
} 
</script>