[SURBL-Discuss] Combined SURBL A record format (Was: Re: BillStearns' sa-blacklistavailable as SURBL: ws.surbl.org)

Scott Truman Scott at ncs.co.nz
Wed Apr 21 22:01:16 CEST 2004

> Hi Scott,
> Multiple A records can result from a single query:
> > % nslookup www.yahoo.com
> > Name:    www.yahoo.akadns.net
> > Addresses:,, 
> > ,,, 
> > Aliases:  www.yahoo.com
> And they should all come from the locally cached copy of the zone
> file, so they're fast.
> A single bit masked A record would be smaller but require a little
> more application CPU to decode.  Multiple A records may be faster
> but they're bulkier.  I find the multiple A records more readable.
> It's one of those classic tradeoffs.
> Jeff C.
So desu ka.

I would have thought that a bit masked record was faster, as you already have all the data you need with the first call. From then on bitwise CPU operations would be umpteen times faster than performing slower DNS callouts, even if they are cached. I am assuming, however, that perhaps the Spamassassin code 'caches' the first A record lookup for bitwise operations...I am not too familiar with the eval-rbl workings. It may be that it performs subsequent DNS lookups in either case? The only way to speed that up would be to load the first lookup into a variable for use in later bitwise calculations...

Anyway keep up the good work all,


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