master mail problems: A temporary workaround

[Lionel Elie Mamane <lionel@mamane.lu>]

On Fri, Dec 09, 2005 at 01:41:55AM +0100, Jeroen van Wolffelaar wrote:
> On Thu, Dec 08, 2005 at 10:33:54PM +0100, Florian Weimer wrote:
>> * Lionel Elie Mamane:
>>> On Thu, Dec 08, 2005 at 09:30:52PM +0100, Wouter Verhelst wrote:

>>>> The fact that my primary MX is only available through IPv6, and
>>>> that this is the case for other people who're having problems too
>>>> might then be a better chance at being the problem.

>>> My primary MX is IPv6-only, too. I don't have detected a problem
>>> yet :)

>> Do you receive lots of mail from master.debian.org, and would you
>> notice the bounces?  Mail from Debian mailing lists come directly
>> from murphy.debian.org, which does not seem to have the problem.

>> You also have one IPv4-only MX, which might be enough to prevent the
>> Exim bug[1] from occurring.

>> [1] I'm not sure if it's a Exim's fault, it's only a hunch.

> I've filed #342619 on the strong suspicion something fishy is going
> on in exim, even though I don't know for sure what's going on
> exactly.

Just a note for fellow DDs that are hit by the problem: A way to
temporarily fix it is to SSH to master and force resolution of your
domain's MXs; for example if your MXs are "foo.example.com" and
"bar.example.org" then do:

 for qtype in A AAAA; do for mx in foo.example.com bar.example.org; do
 dig -t "${qtype}" "${mx}"; done; done

(Hmm... Thinking now that doing the AAAA resolution is probably not
necessary.)

This fix will hold for as long as this information is in master's DNS
cache, thus for at most the TTL of your MX's A entries, maybe shorter
if master's bind decides to throw the information away from the cache
sooner.

Good luck!

-- 
Lionel