BIND vs ncsd

Drew Marshall drew at THEMARSHALLS.CO.UK
Fri Jul 15 09:04:02 IST 2005

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On Fri, July 15, 2005 0:01, Michele Neylon :: Blacknight said:
> On Fri, 2005-07-15 at 08:55 +1000, Peter Russell wrote:
>> Thanks will look at that now. But not just rbls, but i guess every email
>> is subjected to a number of DNS tests, eg PTR lookups?
>> Thanks
> Turn on logging on a DNS server and watch the logs for a few minutes :)
> - just don't forget to turn it off!
> In our experience the DNSBL caching can help speed up mail scanning
> which was our primary concern. We get a lot of DNS traffic anyway, so I
> wouldn't worry about that.

Personally I use DNS Cache which is part of DJBDNS to do all my DNS caching work (I have found it
faster than Bind but YMMV). If you are running all the RBL tests in
SpamAssassin plus getting Postfix to do it's usual PTR lookups and any
other SMTP time checks then you could well be generating upwards of half a
dozen DNS queries per message. With enough volume of mail I could see the
'owner' of a near by DNS server becoming up set :-)

Depending on quantity of mail processed you may well want to look at
holding the RBL, SURBL etc zone files locally and running DNSBL to serve
them so you don't make so many 'cross Internet' zone queries. This will
also speed up your mail processing especially as loads of spam tests seem
to be heading towards DNS style look ups.


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