reverse dns configuration for IPV4, IPV6+ dns+ mail ?

[Reindl Harald]

Am 18.06.2017 um 17:38 schrieb Matus UHLAR - fantomas:
> On 18.06.17 16:26, Mark Elkins wrote:
>> Put two reverse records in both  the IPv4 and IPv6 reverse zones....
>>
>> in the "125.124.123.in-addr.arpa" zone:
>>
>> 126   IN   PTR   mail.xxx.com.
>> 126   IN   PTR   ns.xxx.com.
> 
> while this is possible, it's not always a good idea.
> One reverse record is enough in most cases you need reverse DNS.
> (which mostly means, for outgoing mail)
> 
>> Nothing wrong with a machine (or interface on a machine) having more
>> than one name for the same address. List them all in the reverse
>> configuration. After all, a NS record usually has at least two records 
>> ;-)
> 
> there are cases when having two reverse records is misleading

it's nearly always misleading and results in randomness on the receiving 
server which name get logged and if A/PTR matches

normally you should always have:

* IP with *one* PTR
* the A-Record for the PTR matches
* smtp_helo_name of your MTA matches the same name

and if you have split DNS just make sure that "smtp_helo_name" matches 
what the receiving server would get for a PTR lookup to your public IP 
connecting to him - it's really easy to achieve