On Tue, 17 Dec 1996, Stuart Lynne wrote:
> It would be nice to be able to do spam control from one location.
<details of using DNS snipped>
That is an interesting idea. I know that some sites that want to share
this kind of information are using NIS or NIS+ to do it. Your idea of
using DNS TXT records as a kind of database has a certain attraction.
I would be tempted to add it to Exim as a general feature - a new kind
of lookup - rather than adding a specific sender_host_reject_bydns as
you suggest. You would then say
sender_host_reject = dns;blacklist.poste.com:<other item>:<other item>
The rules for doing that kind of lookup would be just to add the given
extension onto the key, and then look for a TXT record. Hmm. Not quite.
Since DNS domain names have a restricted set of permitted characters,
there would have to be rules for handling the rest. In practice it's
probably only @ that matters, and this could be turned into . as you
suggest.
One disadvantage I see to using this kind of lookup for spam filtering
is that the DNS isn't the sort of thing you really want to be updating
often, at short notice, and slamming in a spam filter quickly is
something one sometimes wants to do. If your mail systems are spread
around a large network with several secondary nameservers, a DNS update
will take some time to propagate.
But the general principle is certainly something I will think about.
Thanks for the suggestion.
I've also noted the idea of using the data returned from a file lookup
for rejection as text to be logged and/or to form part of the error
message.
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Philip Hazel University Computing Service,
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