However on server terminal running;

$ dig @localhost server1.domain.com

; <<>> DiG 9.7.1-P2 <<>> @localhost server1.domain.com
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 20315
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;server1.domain.com.    IN    A

;; AUTHORITY SECTION:
domain.com.        3600    IN    SOA    ns25.domaincontrol.com. dns.jomax.net. 2010072800 28800 7200 604800 3600

;; Query time: 476 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Fri Jan 27 22:35:09 2012
;; MSG SIZE  rcvd: 109

server1.domain.com can be found.

B.R.
SL


From: Juergen Nickelsen <juergen.nickelsen@fu-berlin.de>
To: Stephen Liu <satimis@yahoo.com>
Cc: Squirrelmail User Support Mailing List <squirrelmail-users@lists.sourceforge.net>
Sent: Friday, January 27, 2012 10:21 PM
Subject: Re: [SM-USERS] fail to contact squirrelmail running domain

On 01/27/12 15:19, Stephen Liu wrote:
> # ping server1.domain.com[code]
> ping: unknown host server1.domain.com

So that is the point -- fix your DNS.

--
Juergen Nickelsen <juergen.nickelsen@fu-berlin.de>
Freie Universitaet Berlin, Zentraleinrichtung fuer Datenverarbeitung
Fabeckstrasse 32, 14195 Berlin, Telefon +49.30.838-50740