strange DNS problem

[pckizer at nostrum.com]

On 2006, Oct 6, at 04:02, Wojciech Puchar wrote:
> one of my users reporting problem sending e-mail to @mil.be
> sendmail reports host name lookup failure
> host reports
>
> [wojtek at chylonia ~]$ host -t mx mil.be
> mil.be mail is handled by 10 hermes01.mil.be.
>
> [wojtek at chylonia ~]$ host -t a hermes01.mil.be
> hermes01.mil.be has address 194.7.21.40
> hermes01.mil.be has address 193.191.219.40
> Host hermes01.mil.be not found: 2(SERVFAIL)
> ^^^^^^^^^^^^^
>
> where's a problem? while hostr is able to get IP addresses but then  
> reports servfail?

What you are seeing is the IPv6 AAAA lookup:

# host -t aaaa hermes01.mil.be
Host hermes01.mil.be not found: 2(SERVFAIL)

Make sure you have the Sendmail option turned on to ignore the  
SERVFAIL messages:

# grep AAAA /etc/mail/freebsd.mc
define(`confBIND_OPTS', `WorkAroundBrokenAAAA')

# grep AAAA /etc/mail/sendmail.cf
O ResolverOptions=WorkAroundBrokenAAAA

With that, mail should flow fine.


Though I have to admit I am having a similar problem except the host  
is randomly (with a very high probability of it doing so) failing to  
respond at all rather than at least answering SERVFAIL.  With no  
SERVFAIL it appears Sendmail/resolver consider the NS host to be down  
and do not fail through to try and lookup the A record.  [I'm still  
trying to verify that.]


-philip