* @return false if the user is subscribed, true otherwise
* @throws MessagingException
*/
protected boolean checkSubscriptionStatus(Mail mail) throws MessagingException {
MailAddress mailAddress = mail.getSender();
UsersRepository usersRepository = getUsersRepository();
if (usersRepository.contains(mailAddress.toString())) {
getCommandListservManager().onError(mail,
"Invalid request",
xmlResources.getString("already.subscribed", getStandardProperties()));
return false;
}