Wordpress - Disable user registration password email

You can intercept this email before it is sent using the phpmailer_init hook.

By default, this hook fires before any email is sent. In the function below, $phpmailer will be an instance of PHPMailer, and you can use its methods to remove the default recipient and manipulate the email before it is sent.

add_action('phpmailer_init', 'wse199274_intercept_registration_email');
function wse199274_intercept_registration_email($phpmailer){
    $admin_email = get_option( 'admin_email' );

    # Intercept username and password email by checking subject line
    if( strpos($phpmailer->Subject, 'Your username and password info') ){
        # clear the recipient list
        $phpmailer->ClearAllRecipients();
        # optionally, send the email to the WordPress admin email
        $phpmailer->AddAddress($admin_email);
    }else{
        #not intercepted
    }
}

Actually it depends how you create the new user. If you do it from administration - Users - Add New you are right. In 4.3 unfortunatelly you cannot disable sending the notification email. But if you really want to create a new user without the email, there is a way.

You can create a small plugin where you'd create a new account by yourself via wp_insert_user function, which doesn't send any email by default.

This function can be called like this.

wp_insert_user( $userdata );

Where the userdata parameter is an array where you can pass all needed information.

$userdata = array(
    'user_login'  =>  'login',
    'user_pass'   =>  'password',
);

$user_id = wp_insert_user( $userdata ) ;

//On success
if ( ! is_wp_error( $user_id ) ) {
    echo "User created : ". $user_id;
}

For more informations check codex here.

The wp_new_user_notification function is pluggable, so you can override it by defining your own. You should be able to copy the entire function from wp-includes/pluggable.php into your plugin (or functions.php) and remove the line that sends out the email.