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).
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.
cheers.
eh.
At 18:04 4.7.2000 +0200, Markus Stumpf wrote:
>Hoi folx,
>
>we have the problem that we receive a lot of spam with sender addresses
>e.g. @hotmail.com but the mail is relayed via open relay mailservers
>(not on e.g. mail-abuse RBL).
>
>I think it would not be too hard to hack qmail-smtpd to check for the
>existance of e.g.
> /var/qmail/control/knownsmpt/hotmail.com
>in case the sender domain is hotmail.com, read from the file a list
>of IP addresses and accept the mail, if TCPREMOTEIP is on the list
>or deny it otherwise (hard or temporary, one's milleage may vary).
>
>Has anyone done something like that?
>Any comments (pro/con) on doing somthing like that? (I know it is some
>additional maintenance effort, but maybe one could convince the "big
>mail hosters" to provide such lists for download?)
>
> \Maex
>
>
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