[Gllug] [: qmail, dhcp, dns query]

[Ian Northeast]

bradut at intelesuri.net wrote:
> I have a Debian Woody machine running qmail. It conects to a vigor
> router. I had in /etc/resolv.conf just an entry "nameserver
> [ip_address_of_the_router]"
> This worked fine for browsing the net, but qmail is talking about
> CNAME_failed_temporarily or something like this.
> The machine is on DHCP so I expected to pick it's dns settings
> automatically from the router/[dhcp server] which it does for internet browsing but nor for qmail.
> After putting nameserver entries in /etc/resolv.conf all went ok...
> (proof being this email which has been deilvered and possibly a previous one about a problem which I have sorted by now)

What exactly was it looking up? There are some combinations of records 
(e.g. MX -> CNAME) which are illegal but some nameservers tolerate. Also 
some nameservers may baulk at long chains of CNAMEs, which are legal but 
discouraged. Or if you don't know what it was looking up, where were you 
trying to send mail to? If it was to this group I can't explain it as 
linux.co.uk has 2 MXs both of which point to As which is totally correct 
as would be expected.

The nameserver in the router is likely to be very simplistic. The ones 
you have replaced it with are probably more sophisticated. So it is 
possible that you have hit a combination which is either illegal but 
tolerated by the nameservers you are now using, or too much for your 
router's nameserver to cope with.

IMO the best way is to run your own caching nameserver on your Linux 
box, that way you are in control, you do not depend on your ISP's 
nameservers working, you can debug your problems yourself and if it's 
broken you can fix it.

I might also question why you would want to discard Debian's default 
Exim in favour of Qmail but that's a bit of a religious issue which is 
probably best avoided:)

Regards, Ian (coming to you courtesey of Exim on Debian Woody, and its 
own bind 9.2.1).


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