sendmail does NOT use secondary nameserver

Gregory Hicks ghicks at
Wed Nov 30 21:40:17 UTC 2005

> To: comp-protocols-dns-bind at
> From: Claus van de Vlierd < at>
> Subject: sendmail does NOT use secondary nameserver
> Date: Wed, 30 Nov 2005 20:43:25 +0100
> Hello ,
>   a) in case our primary nameserver works rather slowly
>      our "sendmail" does NOT automatically use  the secondary nameserver.

Two ways to do this:

1.  Put a slave server on the sendmail box and ensure that is
the FIRST nameserver in /etc/resolv.conf ...  In this case, if the
nameserver does not answer, sendmail most probably will not be running
so you'll have bigger problems to contend with.

This method is recommended because the only client the slave should
have is sendmail running on the local box.  This speeds up service.

2.  Put the address of the secondary nameserver as the first nameserver
in /etc/resolv.conf ...  Sendmail doesn't care if the server it queries
is the primary server or a secondary.  All it cares about is whether or
not someone answered.

>      BUT : in the mailer's  "/etc/resolv.conf"  there are both 
> IP-addresses of the prim. and sec. nameserver

There may be other problems.  If you have more than one nameserver
listed in /etc/resolv.conf, the local resolver should automatically go
ahead and query all the nameservers in serial until a) it either gets
an answer, or b) it reaches the end of the nameserver list.  (At least,
this is what MY sendmail does...)

>   (by the way : our browsers have no problems to switch to the sec. 
> nameserver in those cases) .
>   b) can anyone give me "a helping hand" how to make sure that
>      "sendmail" uses for its DNS-queries on port 53 the sec. nameserver
>       in case our prim. nameserver fails ?!
>       (perhaps with some refined "route-statments" in the attached 
> Cisco-Router
> ?!
>    c) thank your for any help !
>      regards ,  Claus van de Vlierd

Gregory Hicks                        | Principal Systems Engineer
Cadence Design Systems               | Direct:   408.576.3609
555 River Oaks Pkwy M/S 6B1          | Fax:      408.894.3400
San Jose, CA 95134                   | Internet: ghicks at

I am perfectly capable of learning from my mistakes.  I will surely
learn a great deal today.

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