[AusNOG] IPv6 reverse DNS and Mail ...

[Mark Smith]

----- Original Message -----
> From: David Miller <dmiller at tiggee.com>
> To: ausnog at lists.ausnog.net
> Cc: 
> Sent: Tuesday, 21 May 2013 2:23 AM
> Subject: Re: [AusNOG] IPv6 reverse DNS and Mail ...
> 
> On 05/20/2013 10:38 AM, Shane Short wrote:
>>  On 20/05/2013, at 6:04 PM, Noel Butler <noel.butler at ausics.net> 
> wrote:
>> 
>>>  On Mon, 2013-05-20 at 16:28 +1000, Reuben Farrelly wrote:
>>> 
>>> 
>>>>  "They don't have a PTR record" isn't an 
> explanation that will cut it to 
>>>>  non IT people, generally, and after the blank look has subsided 
> you'll 
>>>  "Sorry,  but we see that X has failed one of our many anti spam 
> measures so was rejected" - That's good enough. It's been good 
> enough for past near 20 years, fail to see why WE should change, just to appease 
> lazy system admins, if they can't do their job properly, maybe their 
> employers should know, so they can be replaced by someone who will do the job 
> properly.
>>> 
>>  Not to call anyone out in particular, the general contempt some sysadmins 
> show for their users is phenomenal-- sometimes I think people forget why we have 
> these networks in place. We run these networks to service a customer or business 
> need, not to give you toys to play with during the day.
> 
> We do run these networks to satisfy business needs, and one of the
> business requirements passed to 'us' from the 'users' is that 
> they would
> like less spam.
> 

How is lack of PTR an absolute and unquestionable indicator that email from that source is spam?

>> 
>>  If the customer isn't getting their mail, you're not doing your 
> job. You can't dismiss the person with "oh the other end is doing 
> something I don't like so I'm rejecting their email"
> 
> You are looking at this from the wrong perspective.  If the commonly
> accepted requirement for reverse DNS is a huge detriment to message
> flow, then this is a business opportunity.  You should setup an email
> service without this constraint and corner the market for email services.
> 

I think you're looking at it from the wrong perspective. Unless the SMTP RFCs require PTRs (i.e. MUSTs), then dropping email because they don't exist is quite fragile, and placing too much "anti-spam" meaning on the absence or presence of PTRs. Common operational practice doesn't make it a mandatory requirement. You can choose to enforce such a local policy, at the cost of local consequences.

Dropping email because of lack of PTRs is violating Jon Postel's Robustness Principle, which has served the Internet well for decades.

"Be conservative in what you do, be liberal in what you accept from others"







>> 
>>  So what if someone on the other end of the world haven't set up rDNS 
> properly on a box? Google don't set up any rDNS on much of their network 
> infrastructure, which bothers me, shall I blackhole their traffic? I bet 
> that'd last a whole 30 seconds before someone bitches me out.
>> 
>>  -Shane.
>> 
> -DMM
> 
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