function isEmailValid(sEmail) {
	if (sEmail === '') {
		return false;
	}
	
	//Define RegEx string
	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	
	//Test email address
	if (filter.test(sEmail)) {
		return true;
	} else {
		return false;
	}
}