... Interesting problem and resolution.
After further investigation I did find that the Courier you are using has IPv6 support built-in. Of course, as we don't use IPv6 we don't have it built into the kernel. We did have IPv6 support built as a module, but we weren't using it. As a test I loaded module ipv6. Courier then stopped giving me the "DNS lookup failure" messages, however delivery still failed.
Next, I ran /usr/lib/courier/testmxlookup and noticed that the program was hanging. I used strace to see what the hell was going on and noticed that it was in fact trying to use IPv6 first. Also, it was hanging on a sendto() and I noticed that after a while it would try again, but increase the delay used by select() while waiting on the response. Normal DNS usage, but this did let me know that testmxlookup wasn't getting a response back from the DNS server, or was not contacting it properly. Okay, so my next thought was that perhaps the problem is now (after having fixed the IPv6 issue) a DNS resolution issue as testmxlookup is just used to test DNS lookups for the MX record. In /etc/resolv.conf we had:
nameserver 0.0.0.0
This is the usually advised method of defining /etc/resolv.conf when you have a local DNS server. I replaced this with an actual IP address defined on a network interface and now everything works.
So this is something odd going on in Courier.
Anyway, it works now.
I will close out the question in the forum about this issue with a copy of this note.
...
At 03:23 PM 4/3/2003 -0600, Gerardo Gregory wrote:
Unsure of 5.0 (since it is not a stable release but a current one I have not verified if this holds true here also), but on some 4.x versions of FreeBSD I have had issues in the past where my system was doing inet6 queries (AAAA) even though I had disabled it [inet6 that is] (apparently it was not).
Most noticeable in 4.4-release, though. The way I found out about this was doing a tcpdump and catching AAAA queries from the server.
Since then I have disabled IPv6 support (for now anyway) at the Kernel on most of my FreeBSD systems. You can do this by copying one of the Kernel files located at /sys/i386/conf/ and commenting out the inet6 portion. Then doing a config, a make depend, make, make install, and a reboot (to initialize the new kernel). The FreeBSD handbook documentation is pretty thorough on this task, and it is fairly easy to do. If you think this might help, go customize your kernel and see if it gets rid of that problem.
Gerardo
Mitch (WebCob) writes:I'm affraid that's my only idea - I had the same issue, and it was due to DNS not working with IPv6 due to my nameserver config... Maybe you can fix the nameserver that way - I don't think nslookup is an IPv6 tool? So it would use v4 - which obviously works - all I can say is I had the exact same symptoms first time I set up, so I think your options are recompile, or try to determine IF DNS is working under IP6 for you. m/ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Dustin Puryear Sent: Thursday, April 03, 2003 9:01 AM To: Mitch (WebCob) Cc: [EMAIL PROTECTED] Subject: RE: [courier-users] DNS lookup failed? Any other possible issues? We are using the following RPM's: courier-mysql-0.40.0-2.7.3 courier-0.40.0-2.7.3 courier-maildrop-wrapper-0.40.0-2.7.3 courier-smtpauth-0.40.0-2.7.3 courier-webmail-0.40.0-2.7.3 courier-maildrop-0.40.0-2.7.3 courier-pop3d-0.40.0-2.7.3 courier-imapd-0.40.0-2.7.3 courier-mlm-0.40.0-2.7.3 We are using software that installed these particular RPM's. We have heard of nobody else having problems so I wonder if it's not something else? I am not against a recompile, but I'd like to see if there are other options. Any ideas? At 08:20 PM 4/2/2003 -0800, you wrote:Did you remove the ip6 code (there is a configure option for this) - causes issues if memory serves... particularly with DNS lookups I think. m/ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of RICHARD GINZBURG Sent: Wednesday, April 02, 2003 6:25 PM To: [EMAIL PROTECTED] Subject: [courier-users] DNS lookup failed?
Hello all! Whenever I try to send a mail I get DNS lookup failed in the log. I can mail to local account but root:/usr/lib/courier/bin # ./testmxlookup yahoo.com Soft error. Nslookup works: root:/etc # nslookup Default Server: dns.s.bonet.se Address: 212.181.54.2 > set type=mx > yahoo.com ..... mx1.mail.yahoo.com internet address = 64.156.215.5 mx1.mail.yahoo.com internet address = 64.157.4.82 My system is FreeBSD 5.0 and Courier 0.42 What can it be? Thanks! Richard
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