Hi again,
At 22:37 4.7.2000 +0200, Andre Oppermann wrote:
>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?
Yes, I know about that. The other attempt is to use static IP adresses as
Markus' proposed. Both schemes could be combined. Let's assume we have an
additional control file ./stmpallowedfrom:
hotmail.com:195.111.222.200/19 (address range)
fehcom.de:195.162.195.1,195.162.195.2 (list of static ip addresses)
This would give you some possibilty without the need to really now what are
the IP adresses of an SMTP sender. The address parsing is a little tricky.
eh.
>
>> 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
>
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