[SURBL-Discuss] second and third level domains - again!

John Fawcett johnml at michaweb.net
Sun Apr 25 21:22:23 CEST 2004

----- Original Message ----- 
From: "Eric Kolve" 
> On Sun, Apr 25, 2004 at 05:57:56PM +0200, John Fawcett wrote:
> To take care of this in the short term you 
> can add an entry to your spamcop_uri.cf if you 
> have open redirect resolution on:
>   open_redirect_list_spamcop_uri   g.msn.com             ads.msn.co
> I have committed this change to the trunk, so you shouldn't
> have to make the change by hand in the future.

I think you missed my earlier post suggesting this :-)
Thanks for making the update.

> The only way we can take care of this 100% of the time would be
> to query for 2nd - 3rd for TLD and 3rd - 4th for ccTLDs.  This 
> would catch subdomains if those were entered into the RBL.  
> The downside is that this would increase the number of queries
> two fold. We could reduce the queries if we stored a wildcard
> A record for each the 2nd and 3rd level entries and store full entries
> when needed.  Let me illustrate with the following examples:

The mechanism I proposed is an alternative to wildcards and
doesn't have the disadvantage of significantly increasing load.

The client would need a standard logic to query for second level. 
It only increases to third and beyond  where the server
says it has more specific data (by returning an A record with a
specific value agreed for this purpose, e.g.

In the case of a domain of x.co.uk there would only be one extra
query because the client would query co.uk and then because
of the return code it would know to query one level down
x.co.uk. However the query for co.uk will almost certainly
already be cached so the overall impact on client performance
and surbl server load is a mere fraction. Or am I missing 


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