Re: PTR? what the heck is it?
From: Lik Mai Sak (cuddlybear101_at_yahoo.com)
Date: 06/12/03
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Date: Thu, 12 Jun 2003 18:13:48 +1000
On Tue, 10 Jun 2003 15:54:35 GMT
"John Joot" <johnjoot@hotmail.com> wrote:
> ps: again, pls ignore my naivity. if one were to set the TTL to
> zero, why should mail be blocked because of that? i thought TTL (time
> to live) merely tells the DNS server how long (in seconds) to refresh
> record? how would that be associated to potential spam? pls note
> that i set my TTL to 30... the lower the better, right? but too low
> would be too much a strain on the CPU if every record is set that low?
The upstream ISP if a client of mine was using a DNS lookup on all
incoming mail as part of an anti-spam policy. When people from another
company(with TTL=0) sent mail, the ISP's mail server would check to see
that the domain was valid (in order to block spam coming from faked
domains) and rejecting the email as it couldn't verify the domain was
valid.
E.
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