Deliver local mail, DNS-error

Hi,

I'm trying to setup a kolab-server at my home. I recently succeeded to
make the postfix-relay work with my ISP, so I can send mail to external
addresses with postfix. But it won't accept any local mail, throwing a
"Name not found" error as (where compaq is my local hostname and
myhostname.com my internet domain)

postfix/pipe[29437]: 366A672716: to=<[email protected]>,
relay=kolabfilter, delay=1, delays=0.3/0/0/0.74, dsn=2.0.0, status=sent
(delivered via kolabfilter service)
postfix/qmgr[27478]: 366A672716: removed
**postfix/smtp[29442]: A8C4A7277D: to=<[email protected]>,
relay=none, delay=0.55, delays=0.54/0.01/0/0, dsn=5.4.4, status=bounced
(Host or domain name not found. Name service error for name=compaq
type=A: Host not found)**

in /etc/hosts i have a line like, so compaq should be resolved locally:
192.168.1.200	myhostname.com compaq

I tried various settings in /etc/postfix/main.cf for origin, domain and
so on, but the error does not change, so I am missing somethingm but what?

Is this maybe about the virtual-domains thing?

kind regards,
Henning