Mail PTR Records

[Richard Frovarp]

Peter Farrow wrote:
> Matt Kettler wrote:
>> Richard Frovarp wrote:
>>> Peter Farrow wrote:
>>>> Matt Kettler wrote:
>>>>> mikea wrote:
>>>>>> On Mon, Mar 03, 2008 at 01:15:21PM -0600, Nathan Olson wrote:
>>>>>>> It's not RFC-compliant.
>>>>>>
>>>>>> As has been mentioned elsethread, a number of techniques which 
>>>>>> are increasingly necessary for survival are not RFC-compliant.
>>>>>> Many RFCs were written when the Internet was kinder, gentler, and 
>>>>>> MUCH
>>>>>> less dangerous than it is now. They have not changed, though the 
>>>>>> 'Net
>>>>>> certainly has. Blind adherence to them in the face of evidence 
>>>>>> that that adherence opens windows of vulnerability is not 
>>>>>> necessarily dood
>>>>>> or wise.
>>>>>
>>>>> Well, that alone isn't a good reason to blindly toss RFC's aside. 
>>>>> Some requirements of the RFCs are there for damn good reasons.
>>>>>
>>>>> However, in this case I suspect the activity isn't even a 
>>>>> violation of an RFC, and not having a PTR record clearly violates 
>>>>> their recommendations (albeit not their requirements).
>>>>>
>>>>> In general, it's really easy to claim something isn't complaint 
>>>>> with the RFCs without any evidence to support it. We should all 
>>>>> take such suggestions (including those generated by me) as 
>>>>> unsubstantiated opinions until proven otherwise..
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>> http://tools.ietf.org/html/rfc1912
>>>>
>>>> Its an RFC to have a matching forward and revserse DNS lookup, so 
>>>> not having one or a mismatched one is a violation of RFC1912
>>>>
>>>> To quote, verbatim,
>>>>
>>>> "Every Internet-reachable host should have a name. The consequences 
>>>> of this are becoming more and more obvious. Many services available 
>>>> on the Internet will not talk to you if you aren't correctly 
>>>> registered in the DNS. Make sure your PTR and A records match. For 
>>>> every IP address, there should be a matching PTR record in the 
>>>> in-addr.arpa domain."
>>>>
>>>> So you can legitimately bounce the email if the sending host has 
>>>> bad forward/reverse DNS...
>>>>
>>>> Regards
>>>>
>>>> Pete
>>>>
>>> What does "should" mean? should vs shall vs must isn't always the 
>>> same thing.
>>
>> Agreed, should is not the same as must.
>>
>> There's an RFC that specifies exactly how should and must are to be 
>> interpreted in RFC documents.  There is no RFC standard for "shall".
>>
>> http://www.ietf.org/rfc/rfc2119.txt
>>
>>
>> --------------
>> 3. SHOULD   This word, or the adjective "RECOMMENDED", mean that there
>>    may exist valid reasons in particular circumstances to ignore a
>>    particular item, but the full implications must be understood and
>>    carefully weighed before choosing a different course.
>> --------------
>>
>>
>>
>>
> brilliant.  Didn't know about this RFC but I already knew what 
> "should" means...
>
> For those still in any doubt you mind find this page useful,
>
> http://www.englishpage.com/modals/should.html
>
> If you're still having trouble, this may be more appropriate
>
> http://www.bbc.co.uk/cbeebies/metoo/colour/
>
> ;-)
>
 From your site is should: a recommendation, advice, obligation, or 
expectation? Does shall represent: a suggestion, promise, 
predestination, or inevitability? I could interpret should as something 
I must do (obligation) and shall as something I could do (suggestion). 
This would most likely be opposite of expectations and most US legal 
documents, but correct according to the usage of the words. Legal 
documents and specifications must explicitly spell out the exact 
meanings of such words for these reasons. Which is why we have an RFC 
spelling out the meanings of such words.