PTR records for IPv6

Mikael Abrahamsson swmike at
Tue Sep 3 12:52:39 CEST 2013

On Mon, 2 Sep 2013, Mohacsi Janos wrote:

>> Yes, but we must not forget temporary addresses. If the MTA has temporary 
>> addresses, then it will prefer them for its smtp sessions. So, one should 
>> either disable temporaries on all MTAs or use DNS dynamic updates. I think 
>> that it would be much wiser to deprecate PTR checks for IPv6.
> Why would you use temporary address on a defined SMTP server?

Mostly because it's on by default. Even if you configure a static address 
and default gw, as soon as the system sees RAs it might start to use SLAAC 
based privacy addresses for outgoing connections. I've already seen this 
happen once, which caused problems sending mail to google.

Mikael Abrahamsson    email: swmike at

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