On 06/19/2017 01:05 AM, Reindl Harald wrote:

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

This is clear in IPV4 but what about IPV6 ?

If I declare xxx.com bind :

mail A
mail AAAA 2a01:e34:xxxx:xxxx:xxxx:xxxx:1122:3344

ns A
ns AAAA 2a01:e34:xxxx:xxxx:xxxx:xxxx:aabb:ccdd

What should I put for IPV4 reverse address : if I put mail.xxx.com, the reverse address will not point on ns.xxx.com, and if put ns.xxx.com, the reverse dns will not point on mail.xxx.com, and I shall have mail problem.

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