On 5/23/2014 3:02 AM, Joe wrote:
On Thu, 22 May 2014 18:38:37 -0500
John Hasler <jhas...@newsguy.com> wrote:
Joe writes:
But you normally only get one spam at a time from one ISP, which
suggests they do spot the problem themselves fairly quickly...
It suggests that the spammers are quite sophisticated in their use of
their bots.
These are the ones that make it through, meaning among other things
they come from an address with a proper A-PTR record pair.
This depends entirely on how your MTA is set up. Not all MTAs do
reverse domain lookups (they are relatively long time consuming and can
slow down mail processing, especially on a busy system). But even when
they do, most systems nowadays have A-PTR records, even if they are in
the form of "pool-1-1-168-192.example.com".
My rejectlog shows addresses trying several times an hour for days, and
these are mostly domestic users. Presumably most mail servers reject
these, and complaints aren't raised as quickly.
That's just the sender's MTA retrying the request, and has nothing to do
with the spammer. The spammer probably only sent one message. Chances
are the messages are rejected because they're already on someone's
blacklist. Eventually the originating MTA gives up.
Jerry
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