Forgot password

For some reason when I am clicking "Forgot password" and asking the forum to send me a new password, the new password is sent only in one case:
This case is when the email that was filled, is the email of the initial administrator of the forum.
In all other cases the email does not arrive.

You can try it yourself. Register at: http://www.substech.com/dokuwiki/punbb/upload/index.php
Then click "Login" => "Forgotten your password?", and then insert your mail with which you registered. You won't get a new password in your mail box!
What can it be?