Am 19.06.2017 um 08:49 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 "" zone:

126   IN   PTR
126   IN   PTR

Am 18.06.2017 um 17:38 schrieb Matus UHLAR - fantomas:
there are cases when having two reverse records is misleading

On 19.06.17 01:05, Reindl Harald wrote:
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

Even this is not required. In fact, requiring this breaks SMTP RFC.
The only requirement on helo name is that host must exist and be canonical,
which means it has to point to A or AAAA record

should != required
it's best practice

anyways, with 2 PTR records for the same IP on servers with you play lottery because one time it's logged as unknown and the other time as matching, the unknown cases would trigger reject_unknown_client_hostname

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