mail loops back to myself

[Mr. Surachai Sriaram]

hi all
i am install kolabd on debian etch server and newbies on kolabd. i have 
problem when test send e-mail to new kolabd user and test user on example 
data this is error messages
############
Jul  9 14:14:46 knhosp postfix/cleanup[10084]: C8542203413: 
message-id=<20070709071446.C8542203413 at mail.knhosp.go.th>
Jul  9 14:14:46 knhosp postfix/bounce[10086]: A5B4F203412: sender 
non-delivery notification: C8542203413
Jul  9 14:14:46 knhosp postfix/qmgr[10044]: C8542203413: from=<>, size=2262, 
nrcpt=1 (queue active)
Jul  9 14:14:46 knhosp postfix/qmgr[10044]: A5B4F203412: removed
Jul  9 14:14:46 knhosp postfix/smtp[10085]: C8542203413: 
to=<xxx at knhosp.go.th>, relay=none, delay=0.05, delays=0.05/0/0/0, dsn=5.4.6, 
status=bounced (mail for mail.knhosp.go.th loops back to myself)
Jul  9 14:14:46 knhosp postfix/qmgr[10044]: C8542203413: removed
################


this is main.cf configuration file
##########################
knhosp:/# cat /etc/postfix/main.cf
alias_maps = hash:/etc/aliases
#myorigin = /etc/mailname
myhostname = mail.knhosp.go.th
myorigin = /etc/mailname
mydomain = knhosp.go.th
mydestination = $myhostname, $mydomain, localhost.$mydomain, localhost
relayhost =
mynetworks = 127.0.0.0/8, 192.168.1.0/24
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
home_mailbox = Maildir/

virtual_maps = ldap:/etc/postfix/kolab-ldapdistlist.cf, 
ldap:/etc/postfix/kolab-ldapvirtual.cf
transport_maps = ldap:/etc/postfix/kolab-ldaptransport.cf

mailbox_transport = kolabmailboxfilter
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
# Support broken clients like Microsoft Outlook Express 4.x which expect 
AUTH=LOGIN instead of AUTH LOGIN
broken_sasl_auth_clients = yes
############################

how can i fix this problem

thank for advance

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