North American Network Operators Group
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Re: AOL rejecting mail from IP's w/o reverse DNS ?

  • From: Daniel Senie
  • Date: Wed Dec 03 11:07:03 2003 
At 10:42 AM 12/3/2003, Christopher X. Candreva wrote:


On Wed, 3 Dec 2003, Randy Bush wrote:

> you're right.  it will be.  people will have to clean up their
> in-addr.arpa.  or am i missing some reason they can't, other
> than laziness?

See, this is the war I didn't want to start again. Unless I'm thinking of a
discussion on a different list -- I was sure in the whole Verizon "spam
measures hurting other servers" thread, the whole blocking w/o IN PTR
records had come up, with people saying they were on hosting where they
couldn't change PTR records, and the clients who couldn't get mail from
small offices with Exchange servers on DSL lines where the ISP hadn't
configured reverse DNS . Then there was the comment on how reverse DNS was
meaningless, and did you still run identd ?
The issue I think AOL was getting at was not whether PTR records matched the A record for the host. That is indeed a can of worms, and there are reasons why that isn't a good idea, primarily because many people don't have access to the PTR records for smaller blocks or single addresses.

However, there are a great many hosts spewing email (spam, in most cases seen at our servers) that have no INADDR set up at all. It would indeed be helpful if there were reasonable PTR records everywhere, even if the PTR information didn't match the A record information. The PTR information could at least provide some clues as to the ISP involved, etc.


Maybe I'm thinking of the wrong list.

If AOL does it, in a way the question is moot. At least those of us who DO
know how to configure DNS can get some clients from the ones who don't.
Many will turn on a flag to specify "some PTR must exist" if AOL or some other large provider does it and is able to stick with it.

Yes, there'll be some work for DNS-clued consultants if that happens.

The impact on the 'net will not be all that significant, though. A few providers will certainly be impacted, namely those who've not bothered to implement (or only partially implement) INADDR.