out of place mx records.

Andrey G. Sergeev (AKA Andris) andris at aernet.ru
Thu Oct 28 03:46:29 UTC 2010


Hello Gregory,


Thu, 28 Oct 2010 15:54:32 +1300 Gregory Machin wrote:

> Hi Andrey.
> Thanks for you input.
> 
> OK .. but most of those hosts should not be accepting email
> connections, buy my understanding. Or is it implied that email
> destined for that host would be handled by  the email servers
> mcvpemr01 and mcvpemr02 on its behalf ?

Yes. This is a nature of MX RR.

If you don't want to handle mail traffic for some of your hosts (labels
in terms of DNS) at all, then just route your mail as shown below:

; --- Method 1 ---
; This IP should be unreachable or the mail daemon at this host
; should refuse any connections attempts
not-for-mail IN A 192.168.209.16

listserv IN A 202.xx.xx.2
               IN MX 10 not-for-mail

; --- Method 2 ---
listserv IN A 202.xx.xx.2
               IN MX 10 not-for-mail.invalid-domain.tld.

Another but more complex way is to handle such traffic at your mail
relay which is silently delivers messages destined for some domains to
/dev/null.


> Regards
> Gregory Machin
> 
> 
> On Thu, Oct 28, 2010 at 1:09 PM, Andrey G. Sergeev (AKA Andris)
> <andris at aernet.ru> wrote:
>> Hello Gregory,
>>
>>
>> Thu, 28 Oct 2010 13:04:58 +1300 Gregory Machin wrote:
>>
>>> Hi.
>>> I have taken over some dns servers, and the process of doing
>>> upgrade, half way through the process..
>>>
>>> I have a question about the zone files , as there is some
>>> configuration here that I have not seen before and seems out of
>>> place.
>>>
>>> here is an excerpt of the zone file
>>>
>>> $TTL 14400
>>>
>>> @             IN      SOA     example.com. postmaster.example.com.
>>> (
>>>                               2010042142      ; Serial
>>>                               3600            ; Refresh (1 hours)
>>>                               1200            ; Retry   (20
minutes)
>>>                               1728000         ; Expire  (20 days)
>>>                               14400           ; Minimum (4 hours)
>>>                                 )
>>>               IN      NS      ns1.example.com.
>>>               IN      NS      ns2.example.com.
>>> ;             IN      NS      ns1.catalyst.net.nz.
>>>
>>>               IN      MX      10 mail01.example.com.
>>>               IN      MX      10 mail02.example.com.
>>> ;             IN      MX      20 mail03.example.com.
>>>
>>>               IN      A       202.xx.xx.2
>>>
>>> ns1           IN      A       192.168.xx.xx
>>> ns2           IN      A       192.168.xx.xx
>>>
>>> listserv        IN    A       202.xx.xx.2
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>> cache           IN    A       202.xx.xx.1
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>> captaincomet  IN      A       202.xx.xx.1
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>> louie         IN      A       202.xx.xx.1
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>> mail01          IN      A       192.168.xx.xx
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>> mail02          IN      A       192.168.xx.xx
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>> nelson          IN    A       202.xx.xx.1
>>>               IN      MX      10      mcvpemr01
>>>               IN      MX      10      mcvpemr02
>>>
>>>
>>> My question is why would "IN    MX    10    mcvpemr01" and "IN  
>>> MX  10    mcvpemr02" be repeated trough the zone file surely this
is
>>> redundant ?
>>
>> These MX record sets aren't redundant as they belong to the
>> different labels named "listserv", "cache" etc.


-- 

Yours sincerely,

Andrey G. Sergeev (AKA Andris)     http://www.andris.name/



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