2 questions related to mail.

I'm running the Edgy server with ISPConfig setup.

And I have two questions, For some reason my mailserver is no longer sending mail out.
I have always used my ISP as a relay host since they block port 25 for outgoing mail.

I sent a mail to my work 2 hours ago and it still did not arrive, this is very unusual since it usually is instant.
I have also found out that several other mails I send never get there.
From the logs it looks like the mail was handled and accepted by the Relay host.

Code:

Dec  1 22:07:40 lnx1 postfix/smtpd[27675]: 5C118940E3: client=unknown[192.168.1.3], sasl_method=PLAIN, sasl_username=web1_**Removed**
Dec  1 22:07:40 lnx1 postfix/cleanup[27679]: 5C118940E3: message-id=<200612012207.04229.*****@**removed**>
Dec  1 22:07:40 lnx1 postfix/qmgr[2403]: 5C118940E3: from=<**my mail**>, size=931, nrcpt=1 (queue active)
Dec  1 22:07:40 lnx1 postfix/smtpd[27675]: disconnect from unknown[192.168.1.3]
Dec  1 22:07:41 lnx1 postfix/smtp[27680]: 5C118940E3: to=<**my_work_mail**@bt.com>, relay=smtp.orange.nl[193.252.22.245], delay=1, status=sent (250 Ok: queued as F04291C00083)
Dec  1 22:07:41 lnx1 postfix/qmgr[2403]: 5C118940E3: removed

smtp.orange.nl is my Relay host.
I have on purpose removed my username and e-mails.


It might be related to my second question:
Am I an open relay with the standard setup, and becasue of that perhaps the relay host is blackholing my messages?

Reason why I'm asking is something I saw in /var/logs/mail.log while looking for the first problem.

Code:

Dec  1 22:12:28 lnx1 postfix/qmgr[2403]: 4DBF194102: from=<[email protected]>, size=2518, nrcpt=1 (queue active)
Dec  1 22:12:28 lnx1 postfix/qmgr[2403]: 9B563942C8: from=<[email protected]>, size=6543, nrcpt=1 (queue active)
Dec  1 22:12:30 lnx1 postfix/smtp[27759]: 9B563942C8: host smtp.orange.nl[193.252.22.233] said: 450 <[email protected]>: Sender address rejected: Domain not found (in reply to RCPT TO command)
Dec  1 22:12:31 lnx1 postfix/smtp[27758]: 4DBF194102: host smtp.orange.nl[193.252.22.251] said: 450 <[email protected]>: Sender address rejected: Domain not found (in reply to RCPT TO command)
Dec  1 22:12:34 lnx1 postfix/smtp[27758]: 4DBF194102: to=<**forwarding_address**>, orig_to=<**user_on_my_server**>, relay=smtp.orange.nl[193.252.22.245], delay=230999, status=deferred (host smtp.orange.nl[193.252.22.245] said: 450 <[email protected]>: Sender address rejected: Domain not found (in reply to RCPT TO command))
Dec  1 22:12:34 lnx1 postfix/smtp[27759]: 9B563942C8: to=<**forwarding_address**>, orig_to=<**user_on_my_server**>, relay=smtp.orange.nl[193.252.22.234], delay=37865, status=deferred (host smtp.orange.nl[193.252.22.234] said: 450 <[email protected]>: Sender address rejected: Domain not found (in reply to RCPT TO command))

I suspect it is spam getting rejected by my relay host, since the recipiant, is a user on my server that has all her mail forwarded to an external account.

But in any case how can I troubleshoot the first problem to see why my mail is not getting through.