Mail PTR Records

[Peter Farrow]

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/

;-)