sendmail - dns lookup problem

[Viktor Matys <v.matys@grumpa.net>]

Hello,

I have sendmail installed on several servers of different customers.
When I run sendmailconfig on some server I get message:

WARNING: local host name (;; connection timed out; no servers could be
reached) is not qualified; see cf/README: WHO AM I?

As we can see there in brackets is an error message instead of true
local host name. This message is returned from dns lookup procedure. But
dns lookup has no problem (responses are pretty fast):

hostname -f
server.example.com

host server.example.com
server.example.com  has address 10.22.19.126

host 10.22.19.126
126.19.22.10.in-addr.arpa domain name pointer server.example.com

host -t mx example.com
example.com mail is handled by 10 server.example.com.

cat /etc/mailname
server.example.com

That error message appears in some lines in sendmail.cf too:

Dj;; connection timed out; no servers could be reached
Cw;; connection timed out; no servers could be reached
CG;; connection timed out; no servers could be reached

I must repair sendmail.cf myself "by hands", but Debian has "helpful" 
feature - after reboot is sendmail.cf autogenerated with those error 
messages inside again.

Why sendmailconfig cannot see true server name?

Thank you very much

Viktor Matys