[AusNOG] IPv6 reverse DNS and Mail ...

[Karl Auer]

On Tue, 2013-05-21 at 17:06 +1000, Noel Butler wrote:
> quick look at yesterday on just one box 
> 5xx Reject unknown client host              45.71%
> 
> That's a rather large chunk of trash that amavisd doesn't have to look
> at

Except, of course, that you don't know it's all trash. Which is the
point.

> I know, my bad for suggesting somebody actually do some
> work :)

I don't think anyone disagrees with the fact that it is, in the great
scheme of things, pretty easy to add a PTR record. Nonetheless, it may
be hard for some legitimate senders, and more so as IPv6 ramps up, who
you will then punish by dropping their emails.

The point I and others are trying to make is that making rDNS entries
for this reason is basically makework - it is necessary ONLY to identify
a mail server as one where somebody did that little bit of extra work. A
sort of binary marker. It has no necessary technical functionality at
all[1]. If as I expect (because it is happening already) IPv6 rDNS ends
up fully synthesised, it will be a completely pointless marker.

Regards, K.

[1] This is not to say that rDNS has no use. It's cool from an
informational point of view to be able to see who an address range
"belongs" to, helpful in traceroutes and so forth. But it's not
*necessary*.


-- 
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Karl Auer                                          tel  +61-2-64957435
kauer at into6.com.au                                 mob  +61-428-957160
                                         
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