Minimum TTL?

John Levine johnl at
Sat Feb 10 19:18:29 UTC 2018

In article <mailman.463.1518283598.749.bind-users at> you write:
>The target, instead of very quickly rejecting the spam because of the =
>lack of a domain or the lack of DNS, instead has to deal with thousands =
>of different IPs.

That's not how spam filters work.  They do filtering based on the IP
address sending the spam and maybe the rDNS.  It makes no difference
whatsoever if there is some other random A record pointing at the
spamming host.  You can't even tell.

>> Botnets are computers with IP addresses.  They don't need DNS pointing =
>at them to send spam.
>They do to send spam to any mail admin with even half a brain who would =
>not accept unauthenticated mail from an IP without an actual domain =

The half a brain generally requires forward and reverse DNS to match
before using them.  If you know a way to do fast flux rDNS on botnets,
I know a lot of people who'd like to talk to you.


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