Zombie Changes to Domain/Host Name in Mail Settings Window

Question

For the second time since setting it up, the domain name has changed from "domain.com" to "local", and the host name has changed from "myserver.domain.com" to "myserver.local".
This tends to screw up my mail services.
I cannot determine why this would change, by itself, without any external intervention from anyone.
Suggestions?

Answer 1

Thanks for your reply!
The server is configured with static IP and running DHCP, DNS and mail, connectet to a D-Link router (the router also acting as a firewall). The DNS is configured with forwarder IP-addresses to the ISP and Google. Domain/hostname is changed from server.ljungh.net to server.local in postfix/main.cf (and other config files) and triggered if internet connection is lost by rebooting the router (or if internet connection to ISP is down for some other reason). Everything is working fine as long as the internet is up and running. The server is not acting as a firewall or multiple-network-controller.
Output from changeip -checkhostname:
Primary address = 192.168.0.196
Current HostName = server.ljungh.net
DNS HostName = server.ljungh.net
The names match. There is nothing to change.
dirserv:success = "success"
Output from dig server.ljungh.net:
; <<>> DiG 9.6.0-APPLE-P2 <<>> server.ljungh.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61515
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;server.ljungh.net. IN A
;; ANSWER SECTION:
server.ljungh.net. 10800 IN A 192.168.0.196
;; AUTHORITY SECTION:
ljungh.net. 10800 IN NS server.ljungh.net.
;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sun May 30 16:45:38 2010
;; MSG SIZE rcvd: 65
Output from dig -x 192.168.0.196:
; <<>> DiG 9.6.0-APPLE-P2 <<>> -x 192.168.0.196
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27573
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1
;; QUESTION SECTION:
;196.0.168.192.in-addr.arpa. IN PTR
;; ANSWER SECTION:
196.0.168.192.in-addr.arpa. 10800 IN PTR server.ljungh.net.
;; AUTHORITY SECTION:
0.168.192.in-addr.arpa. 10800 IN NS server.ljungh.net.
;; ADDITIONAL SECTION:
server.ljungh.net. 10800 IN A 192.168.0.196
;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sun May 30 16:46:01 2010
;; MSG SIZE rcvd: 105