Erwin Hoffmann wrote:
>
> Hi,
>
> since I'm dealing with the SPAMCONTROL patch, I would like to comment your
> problem:
>
> 1. You are right. Within the filtering mechanisms a logical "AND" scheme is
> missing. To implement this requires some attention.
>
> 2. Principally the following checks could be applied:
>
> Logic:
> a) The envelope's MAIL FROM: address has to be taken.
> b) From TCPENV the REMOTEIP has to be taken (=> real Sender IP)
> c) By means of a DNS A-Lookup(MAIL FROM: address) the (let's call it)
> pretended IP address has to be evaluated.
>
> Assumption:
> For legitamate E-Mails both IP addresses belong (usually) to the same IP
> subnet. However, one has to define a range of significant IP address bits
> to evaluate (common in the CIDR scheme).
Unfortunatly this assumption is pretty much flawed. For example I have
two IP ranges, 195.134.128/19 and 62.48.0.0/19. Now my customers are
usually in the 195 range but my mail servers are in the 62 range. So
how do you propose to handle that?
> Result:
> => Comparing both IP addresses would effectively eliminate reception of
> E-mail thru 3rd party relays, as in your case.
>
> I think about but don't promise anything. There are other items on my agenda.
--
Andre
