function isEmailValido(emailStr) {

	/* regexp usuario@dominio */
	var emailPat=/^(.+)@(.+)$/;
	
	/* caracteres especiais ( ) < > @ , ; : \ " . [ ] */
	var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";
	
	/* regexp de caracteres invalidos */
	var validChars="\[^\\s" + specialChars + "\]";

	
	/*  E.g. "jiminy cricket"@disney.com */
	var quotedUser="(\"[^\"]*\")";
	
	/*  joe@[123.124.233.4] is a legal */
	var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;


	
	/*  non-special characters */
	var atom=validChars + '+';
	
	/* john.doe@somewhere.com, john and doe are words. */
	
	var word="(" + atom + "|" + quotedUser + ")";
	
	// estrutura do nome do usuario
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
	
	// estrutura do nome de dominio 
	var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");
	

	var matchArray=emailStr.match(emailPat);

	if (matchArray==null) {
		displayEmailInvalido(); 
		return false;
	}

	var user=matchArray[1];
	var domain=matchArray[2];


	for (i=0; i<user.length; i++) {
		if (user.charCodeAt(i)>127) {
			displayEmailInvalido(); 
			return false;
	   	}
	}

	for (i=0; i<domain.length; i++) {
		if (domain.charCodeAt(i)>127) {
			displayEmailInvalido(); 
			return false;
	   	}
	}

	if (user.match(userPat)==null) {
		displayEmailInvalido(); 
		return false;
	}

	// Domain is symbolic name.  Check if it's valid.
	 
	var atomPat=new RegExp("^" + atom + "$");
	var domArr=domain.split(".");
	var len=domArr.length;

	for (i=0;i<len;i++) {
		if (domArr[i].search(atomPat)==-1) {
		displayEmailInvalido(); 
		return false;
   		}
	}

	// Make sure there's a host name preceding the domain.

	if (len<2) {
		displayEmailInvalido(); 
		return false;
	}

	// se chegou aqui, eh valido
	return true;
}


// funcao para mostrar o erro de validacao do email
function displayEmailInvalido() {
	showAlert("E-mail inválido.");
}