name lookup failed, Sendmail 8.11.x, IPv6

Kevin Darcy kcd at daimlerchrysler.com
Fri Aug 10 22:16:38 UTC 2001


If either of these claims are true, then they must be very recent additions,
since my 8.11.2 mail servers have no problems with "reverse-less" destinations,
and they generate no AAAA queries.

I don't think either of those assertions are very credible, though. If true,
they would cause massive breakage all over the Internet. As for the AAAA claim,
why not just look at your query logs and see if sendmail is generating AAAA
queries. As for the "reverse-less destination" claim, look more closely at the
bounce message. I suspect that it's probably more a case of the destination
server not being able to reverse-lookup the sending server (i.e. your relay)
than the other way around.


- Kevin

Robert Wood wrote:

> [ This is a repost of the following article:                               ]
> [ From: Robert Wood <usenet at woodstea.com>                                  ]
> [ Subject: name lookup failed, v8.11.x, IPv6                               ]
> [ Newsgroups: comp.mail.sendmail                                           ]
> [ Message-ID: <9l12g6$13p1$1 at nntp1.ba.best.com>                            ]
>
> I'm looking for some help with messages that my mail relay is sending
> out, that are being bounced back because of DNS problems. My mail
> relay appears to be complaining when the destination server (the
> one from the MX record) does not have a valid reverse entry for its
> IP address.
>
> Why should this be a problem? I though that a mail server was only
> concerned about the reverse lookup when *receiving* mail from
> another host.
>
> Now, I recently heard that there was a problem in Sendmail 8.11
> involving IPv6 lookups. The idea was that Sendmail would first try
> to do an AAAA lookup on the destination host, and this would fail,
> causing the mail to be rejected with a "name lookup failed" error
> message. So the problem isn't that my mailer is trying to do a
> PTR lookup, but that before it does an A lookup for the host in
> the MX record, it's first trying an AAAA lookup and that's what
> makes it fail.
>
> Has anyone heard of this? I am running Sendmail 8.11.3, BIND 8.2.3
> resolver.
>
> Example domain: americantower.com
>
> > dig americantower.com mx
>
> ; <<>> DiG 8.3 <<>> americantower.com mx
> ;; res options: init recurs defnam dnsrch
> ;; got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4
> ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 3, ADDITIONAL: 6
> ;; QUERY SECTION:
> ;;      americantower.com, type = MX, class = IN
>
> ;; ANSWER SECTION:
> americantower.com.      1H IN MX        30 mail207.americantower.com.
> americantower.com.      1H IN MX        10 mail1.americantower.com.
> americantower.com.      1H IN MX        20 mail2.americantower.com.
>
> ;; AUTHORITY SECTION:
> americantower.com.      1H IN NS        ns1.americantower.com.
> americantower.com.      1H IN NS        ns2.americantower.com.
> americantower.com.      1H IN NS        ns4.americantower.com.
>
> ;; ADDITIONAL SECTION:
> mail207.americantower.com.  1H IN A  207.175.1.149
> mail1.americantower.com.  1H IN A  64.212.196.19
> mail2.americantower.com.  1H IN A  64.212.196.149
> ns1.americantower.com.  1H IN A         64.212.196.9
> ns2.americantower.com.  1H IN A         64.212.196.118
> ns4.americantower.com.  1H IN A         24.94.152.130
>
> ;; Total query time: 5075 msec
> ;; FROM: xxxx to SERVER: default -- 127.0.0.1
> ;; WHEN: Fri Aug 10 11:26:58 2001
> ;; MSG SIZE  sent: 35  rcvd: 253
>
> > nslookup 64.212.196.19
> Server:  localhost
> Address:  127.0.0.1
>
> *** localhost can't find 64.212.196.19: No response from server
>
> Thanks,
> Rob





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