[Pdns-announce] Interoperability problem between Microsoft Azure DNS and Exchange and PowerDNS Recursor and IPv6 + solution

bert hubert bert.hubert at netherlabs.nl
Wed Dec 3 18:43:13 UTC 2014

Hi everybody,

Yesterday we worked with various providers to debug a problem between
Microsoft Exchange, PowerDNS Recursor and the Microsoft Azure nameservers.

If you or your users employ Microsoft Exchange on IPv6 and see email
delivery problems to domain names hosted on Azure, this message is for you.

The problem is that the Azure nameservers send out 'lame' replies for AAAA
queries. PowerDNS converts these lame answers into a servfail. This in turn
leads Microsoft Exchange connected to IPv6 to refuse to deliver email.

We have notified Microsoft of the issue, but it may take them some time to
fix it. Meanwhile however we've written a small Lua script that converts
specific SERVFAIL responses so Exchange likes them.

http://pastebin.com/g16tyCU5 has the script, and you can modify or copy line
15 to fix up domains relevant for you (so add multiple lines for other
domain names).

We want to thank Jussi from Finland for helping us debug this problem.

Good luck!


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