how to validate the textbox data is in emailformat or not using errorprovider1 control

function isEmail(argvalue) {

  if (argvalue.indexOf(" ") != -1)
    return false;
  else if (argvalue.indexOf("@") == -1)
    return false;
  else if (argvalue.indexOf("@") == 0)
    return false;
  else if (argvalue.indexOf("@") == (argvalue.length-1))
    return false;

  // arrayString = argvalue.split("@"); (works only in netscape3 and above.)
  var retSize = customSplit(argvalue, "@", "arrayString");

  if (arrayString[1].indexOf(".") == -1)
    return false;
  else if (arrayString[1].indexOf(".") == 0)
    return false;
  else if (arrayString[1].charAt(arrayString[1].length-1) == ".") {
    return false;
  }

  return true;

}