SERVFAIL?!

[David Brueckmann]

I have a customer with a mailserver (sendmail) connected via dialup 
running. There is a local named on this machine with the following 
named.boot-file:

---
primary         10.in-addr.arpa db.10
forwarders 151.189.26.245
forwarders 151.189.13.25
forwarders 151.189.0.25
options forward-only
slave
---

I need the forwarders because these are the only nameservers this
machine can reach.

The problem is: Sometimes (every 4-5 days) there are many entries like

named[130]: sysquery: findns error (SERVFAIL) on mailin01.btx.dtag.de?

in my syslog and the machine dials up about 40 times per day.

What is the problem? Any idea?


bye & thx,
dave