// Check for valid e-mail address

function checkEmail(email1, email2) {
  var index1 = email1.indexOf("@");
  var index2 = email2.indexOf("@");
  if(!(index1 > 1 && index1+1 < email1.lastIndexOf("."))) {
    alert('Error: please fill in the e-mail address of the travel agent correctly.');
    return false;
  }
  if(!(index2 > 1 && index2+1 < email2.lastIndexOf("."))) {
    alert('Error: please fill in your e-mail address correctly.');
    return false;
  }
  if(index1 > 1 && index1+1 < email1.lastIndexOf(".")) {
    return true;
  } else {
    alert('Error: invalid e-mail address. Please check.');
    return false;
  }
  if(index2 > 1 && index2+1 < email2.lastIndexOf(".")) {
    return true;
  } else {
    alert('Error: invalid e-mail address. Please check.');
    return false;
  }
}