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Re: TXT Records

2003-11-20 07:50:50
A "txt" lookup will generally be a miss as well and thus negatively 
cached so I don't think your argument is valid.

Good point, at least initially.  Over time this will hopefully cease
to be the case.

Actually, even if the negatively cached record expires from the cache,
the NS servers for the domain will still be cached, so the lookup
should be quick.

Actually, the big problem with doing any DNS lookups at all is for
sites with broken DNS.  In many cases you'll have to wait tens of
seconds for the lookups to time out and give SERVFAIL.

This isn't helped by the practice of a number of ISPs of 'suspending'
domains of spammers by pointing them at non-existent nameservers,
therefore guaranteeing that all DNS lookups will time out.

Of course, anyone who checks that the sender's address is resolvable
already faces this problem.  (Most big ISP's don't at the moment,
though.)

        -roy

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