[AusNOG] IPv6 reverse DNS and Mail ...

Jeremy Visser jeremy at visser.name
Mon May 20 14:46:36 EST 2013


On 20/05/2013, at 1:55 PM, Terry Sweetser (SkyMesh CTO) <terry+AusNOG at skymesh.net.au> wrote:
> At SkyMesh, we routinely get "submissions" from remote mail admins to stop blocking their email.
> 
> It turns out on many occasion that the remote site has ipv6, no reverse dns, and is connecting to our MX farm on ipv6.

I see this most often on 6to4 which some routers either set up by default or make it very easy to turn on (Apple AirPort, I'm looking at you — yes, some people run these in front of a mail server).

I suspect this is the reason why MS Exchange defaults to IPv4 outbound e-mail, even if IPv6 is available. The only way I've figured out how to convince Exchange to send out via IPv6 is by sending to an IPv6–only MX.




More information about the AusNOG mailing list