>I looked through the log for the time period (9:20 to 9:30) and found lots
>of hotmail messages that went through, but no attempts to deliver a message
>to mailbox [EMAIL PROTECTED] So, if we had a problem with one
>of our DNS server (the one operated by separate ISP), then that could
>explain this kind of behavior?
Yes, it would. It looks like Hotmail was going to another mailserver other
than yours. Either it is a glitch on their end, or there was a DNS problem
pointing them to the wrong mailserver.
> My assumption is that hotmail sometimes
>connects to the "good" DNS server and sometimes connects to the "bad" one.
That sounds like it may be the case.
>Now the second DNS server does correctly lookup our domains, but it is not
>listed as authoritative (according to dnsreport.com). Why is that bad?
All DNS servers in the world are either authoritative for
distinctivefeatures.com (about 1-3 DNS servers, usually), or they are not
(the millions of other DNS servers).
If Hotmail connects to any of the authoritative nameservers for the domain,
the authoritative nameserver will respond immediately with an answer. An
authoritative nameserver check with the primary DNS server every so often
to make sure that it has the latest data.
If Hotmail connects to any other DNS server (such as the one listed at the
root servers), that server will act like any other DNS server -- it will
look up the information at the root servers to find out what nameserver to
go to, and so forth. However, what happens when this DNS server goes to
the root servers, and the root servers tell it to ask itself for the
information? You could have an infinite loop (fortunately, all DNS servers
should be smart enough to check with the other NS records in this case).
>I mean, why wouldn't hotmail be just as happy with a look-up from a
>non-authoritative DNS server?
It should be -- it really shouldn't care. But maybe it does (if it looks
closely at the answer it gets, it will know that it is dealing with a lame
delegation). Or maybe this lame nameserver reported an error. Or maybe it
was just giving out bogus information.
-Scott
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