Log messages except some categories

Hi! im logging all erors and warnings, and sending to email. Problem is if someone, for example, accessing not existing page (404) , i get email. And yesterday google spider was trying to access robots.txt and i didn't have that. So i got 35 emails ;/ and one problem to resolve with message logging. As you understand problem is not in robots.txt file but in general. someone wants to get some page , it doesnt exist and it goes to email. not cool

and question is How can i ignore some cateories rom log router defined categories?

        'log'=>array(
            'class'=>'CLogRouter',
            'routes'=>array(
                array( 
                    'class'=>'CFileLogRoute',
                    'levels'=>'error, warning', //logging all errors and warnings
                ),
                array(
                    'class'=>'CEmailLogRoute',
                    'levels'=>'error', // send to emails only errors
                    'email'=>'admin@example.com',
                    'categories'=>'!exception.CHttpException.404' // and here i want to put ignore statement to not send 404 errors
                ),
            ),
        ),

can i do that somehow?
or there i should do some workaround.
maybe i can remove " exception.CHttpException.* " from error category. this would resolve my problem as well.