ncache support for dnscache?

Hi there

We are keen users of Spamassassin, and that means tonnes of RBL DNS
lookups. And that means tonnes of lookups from New Zealand over large
stretches of high-latency links to US and European DNS servers...

A huge number of those DNS RBL lookups don't get a match - but as the
response is a "negative", it's not cached by dnscache, as dnscache
doesn't support the (RFC optional) DNS NCACHE option for storing a
failed lookup with some small TTL. So the next mail comes in and the
same lookups happen all over again. I can compare the performance of our
US-based SA servers against our NZ-based ones: the US ones average 0.3
secs per message - our NZ ones average 3 sec... Factor of 10 difference,
and 99% of that is DNS related (i.e it ain't hardware or network congestion)

Has anyone written a patch for dnscache to do this, and is there a 
reason why I haven't found it in Google? i.e. is there a good reason why
dnscache doesn't do this that I haven't figured out yet 

Thanks

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Cheers

Jason Haar
Information Security Manager, Trimble Navigation Ltd.
Phone: +64 3 9635 377 Fax: +64 3 9635 417
PGP Fingerprint: 7A2E 0407 C9A6 CAF6 2B9F 8422 C063 5EBB FE1D 66D1