user validation messages

Permalink
running c5 ver 8.10

In Dashboard "login & registration"/"Public Registration" I've set true to "Validate - anyone can create an account from Login page, once validated by email"

In application\config I've set concrete.php as follows:

<?php
return array(
    'email' => array(
        // The system default sender (Group A)
        'default' => array(
           'address' => 'noreplay@xxx.org',
            'name' => 'xxx.org', // this can be left out
        ),
        // The individual senders (Group B)
        // Form block:
        'form_block' => array(
            'address' => 'noreplay@xxx.org',
        ),
        // User registration email validation messages
        'validate_registration' => array(


THE PROBLEM
First: after user confirmed the mail, C5 sends "after validation" a notification mail (not requested!) with mail sender address the mail address of administrator, and not 'noreplay@xxx.org'

Second: it happens on some of my sites (same architeture and version) that C5 sends the request of validation and, after a minute or two, the notification mail: so user do not explicitally click on request of validation but are validated automatically.... How can it happen ?

Thank you so much for help