Correct me "Function of Mail alias module " if i am wrong

Currently, all the mailalias module does is to check to see that each email address is valid before setting a user property.

The code is here: http://cvs.drupal.org/viewcvs/contributions/modules/mailalias/mailalias....

It is a very small module. Here's the entire module:

// $Id: mailalias.module,v 1.9 2004/10/01 21:51:48 ankur Exp $

function mailalias_user($type, &$edit, &$user, $category = NULL) {
  if ($type == 'form' && $category == 'account') {
    // when user tries to edit his own data $output =
    $output = form_textfield(t('Email aliases'), 'mailalias', $user->mailalias, 70, 255, t('Add any additional email addresses, separated by commas. We use these to identify the author of email submissions. These email addresses are private and are not shared with other users.'));
    return array(array('title' => t('Personal information'), 'data' => $output, 'weight' => 2));
  }
  else if ($type == 'validate' && $category == 'account') {
    $mailalias = strtr($edit["mailalias"], array (" " => "")); // strip spaces
    $mailsarr = explode(",", $mailalias);
    foreach ($mailsarr as $mail) {
      if ($mail != null && $error = user_validate_mail($mail)) {
        form_set_error(t('Mail Alias'), $error);
      }
    }
    return $edit;
  }
}

function mailalias_help($section) {
  if ($section == "admin/modules#description") {
    return t("A user may associate additional email addresses with his account.");
  }
}

As you can see, it merely calls user_validate_mail($mail) for each email address specified. This function calls valid_email_address($mail), which just validates the format of the email address without checking the database.