email problem, latest ISPC3 on debian squeeze

[manarak]

I followed the perfect server tutorial for installing ISPC3 on debian squeeze.

I've got a rather strange problem.

I can receive email from outside
I can send to other email accounts on the server

BUT:
I can't send mail to outside of the server.
Nor by sendmail nor by SMTP (Outlook).

There is nothing in the mail errors log, the following is in the mail info log:

Jun 7 18:15:04 hostname postfix/smtp[13530]: 706A210421D8: to=<webmaster@***.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.84, delays=0.47/0.01/0/0.36, dsn=2.0.0, status=sent (250 2.0.0 Ok, id=23081-18, from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as 2866F10421D9)
Jun 7 18:15:04 hostname postfix/qmgr[31595]: 706A210421D8: removed
Jun 7 18:15:04 hostname postfix/pipe[13556]: 2866F10421D9: to=<webmaster@***.com>, relay=maildrop, delay=0.05, delays=0.01/0.01/0/0.03, dsn=2.0.0, status=sent (delivered via maildrop service)
Jun 7 18:15:04 hostname postfix/qmgr[31595]: 2866F10421D9: removed

so... the server thinks the message has been sent.