Re: Reverse IPv6 DNS checks on ietf MXs?

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Tim Chown wrote:
[...]
> It's not uncommon for IPv6 servers to be multiaddressed, so mail admins
> will probably just need to be a wee bit more careful, and certainly try
> to avoid using autoconf globals on servers.

Nothing wrong with EUI-64 or autoconf, as long as you actually want them
there ;)

and otherwise on eg Linux:
net.ipv6.conf.default.accept_ra=0
net.ipv6.conf.all.accept_ra=0
other mechanisms hopefully available on your favourite OS.

As for the IETF mailservers rejecting it, clearly there was a
misconfiguration and they caught that perfectly fine. Misconfigured
boxes should not be able to send out mail, there is most often other
things also misconfigured then and/or they are not monitored and thus
just used for abuse.

> In our case our server
> acquired an additional global autoconf address on top of its manually
> configured address, which it started sending from, and as this had no 
> reverse DNS entry we encountered the Rejects.

I suggest installing NDPMon (http://ndpmon.sourceforge.net/) next to
your arpwatch that you should have running for IPv4. Of course
protecting your L2 with 802.1x or a similar system next to that is also
a good hint.

BTW: for postfix, smtp_bind_address6 allows you to fix the outgoing
address to a certain IP (smtp_bind_address for IPv4 ;)

Greets,
 Jeroen


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