Bugtraq: Re: Is predictable spam filtering a vulnerability?

[Jon Fiedler <jmf9 () cwru edu>]

David F. Skoll wrote:

> On Wed, 16 Jun 2004, R Armiento wrote:
>
>  
>
> > However, 'C':s spam filter silently drops the email.
> >    
> In my opinion, any spam filter that silently drops e-mail is broken, and
> is indeed a security risk.  A spam filter MUST respond with a 500 SMTP
> failure code if it rejects a message.
>
> Regards,
>
> David.
>  
This ignores client side spam filters, and doesn't really change the 
attack.  The 500 message would be sent back to A, but not B, so B is 
still in the dark about C not receiving the emails.
jon