Ongoing named trouble
I have, for quite some time, had trouble with my BIND installation
falsely claiming that certain domains don't exist. It tends to be
pretty consistent about them - anything under yahoo.com can be counted
on to display this, for instance.
The symptom, which is primarily noticable for outgoing email (handled
by exim) and web browsing (netscape or mozilla), is that the first
attempt to resolve the domain gets a 'not found' response, but
retrying immediately afterward works fine. The domain then works
properly for a while (presumably until the information on it gets
dropped from BIND's cache), then it gives the spurious 'not found'
again. This is presumably a timeout issue, but I haven't been able
to verify that theory.
For web browsing, it's an annoyance, but not a big deal - just
resubmit the request and it works the second time. In mail, however,
it's more significant... It started out with just getting
'non-routable mail domain' bounces and resending the message, but now
I'm running a mailing list with a couple subscribers from UK domains
that display this problem and Mailman eats the bounces, so there's no
way to even detect when it happens until someone looks at the list
archive and notices that there are archived messages which he never
received.
In my attempts to resolve this problem, I've updated my root hints
and double-checked that I'm set to use my ISP's name servers as
forwarders and that they work properly. (Interestingly enough,
testing them again just before sending this message, both of the ISP
nameservers resolved mail.yahoo.com instantly, but mine took several
seconds to do so. Trying it again after a BIND restart, the first
attempt came back with "can't find mail.yahoo.com: Non-existent
host/domain" after 15 seconds on the first try, found the address
after 5 seconds on the second try, and responded instantly on the
third. This is repeatable.)
What do I need to do to my configuration, whether of BIND or of exim,
to make mail delivery bit more reliable? I would, ideally, like to
fix this in BIND, of course, but at this point I would settle for a
configuration setting to tell exim to always try delivery twice, even
if the first attempt gets a 'Non-existent host/domain' error.
--
The freedoms that we enjoy presently are the most important victories of the
White Hats over the past several millennia, and it is vitally important that
we don't give them up now, only because we are frightened.
- Eolake Stobblehouse (http://stobblehouse.com/text/battle.html)
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