using API in postHooks failing

mail('me@mydomain','result', 'user='. $hook->getValue('username') );

mail('me@mydomain','result', 'user=' );

$message = 'Hi, a new User signed up: '.$hook->getValue('username')
 . ' with email '.$hook->getValue('email').'.';
$modx->getService('mail', 'mail.modPHPMailer');
$modx->mail->set(modMail::MAIL_BODY,$message);
$modx->mail->set(modMail::MAIL_FROM,'me@mydomain');
$modx->mail->set(modMail::MAIL_FROM_NAME,'Jerrys Site');
$modx->mail->set(modMail::MAIL_SENDER,'Jerrys Site');
$modx->mail->set(modMail::MAIL_SUBJECT,'New User Signed Up');
$modx->mail->address('to','me@mydomain');
$modx->mail->setHTML(true);
if (!$modx->mail->send()) {
    $modx->log(modX::LOG_LEVEL_ERROR,'An error occurred while trying to send the email: '.$err);
}
$modx->mail->reset();
/* tell our snippet we're good and can continue */
return true;

$username = $hook->getValue('username');
mail('me@mydomain','result',"user=$username");

$email = $hook->getValue('username');
$hook->setValue('email',$email);