ben at adversary.org
Thu Jun 1 10:25:21 CEST 2017
On Tue, May 30, 2017 at 09:27:30PM -0400, Daniel Kahn Gillmor wrote:
> On Wed 2017-05-31 10:02:16 +1000, Ben McGinnes wrote:
>> It is pretty standard (and IIRC part of the SMTP RFCs) that the
>> forward and reverse DNS records must match. The PTR record does not
>> have to match the hostname, but it does have to resolve to a hostname
>> with an A record pointing back to the IP.
>> That lack of a PTR record for 184.108.40.206 will definitely cause
>> problems with any number of SMTP servers.
> i'm aware of this common convention (without commenting on how useful it
> is at actually defeating spammers),
It may or may not be quite so useful now, but in the past it was a
good way of catching out connections from dynamically assigned IP
addresses. Usually an SMTP connection from such a host meant a
compromised Windows box, the chances of it being a Linux enthusiast
were very slim.
Regardless of whether it remains useful, I'm sure most mail
administrators will retain that check since there's no reason not to.
> but i'm surprised to see it happening with two mail servers that
> both have sent messages to GnuPG mailing lists in the
> not-too-distant past. it's possible that both of those mailservers
> have changed at the same time, i guess. there certainly was a
> recent change for my own mail relay.
This I'm less sure on given how much is attached, either intentionally
or not, to the Internet these days. I'm somewhat less surprised by
demonstrations of technical ignorance now. I chalk that up to having
spent too long working in the industry.
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