Exchange 2007 No Longer Receiving External Email

Hello, I am having a strange problem as this server was configured and working 3 days ago is not getting any external email. It was working fine Friday night and now if try to send from Exchange server, the messages just sit in the queue and are not able to be delivered. I have not changed anything and as far as I know, nothing else has changed anywhere. Is there somewhere in Exchange 2007 that I can control the connections like I did in Exchange 2003? I cannot find what the issue is and have run out of places to look.

Also, if this helps, When I run a telnet test, everything is Ok until to try to email my self from the problem server and I get, Unable to relay. Where is that being controlled at?

Here is the Telnet test I did.

220 mail.domain.com Microsoft ESMTP MAIL Service ready at Mon, 11 Jul 2011 13:
25:10 -0400
ehlo
250-mail.domain.com Hello [x.x.x.x External IP]
250-SIZE 10485760
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-AUTH
250-8BITMIME
250-BINARYMIME
250 CHUNKING
mail from:administrator@domain.com
250 2.1.0 Sender OK
rcpt to:email@externaldomain.com
550 5.7.1 Unable to relay

Thank you in advance for any help....

I am not confirmed about it but I think there will be an error at your ISP preventing email prior toward getting your Exchange server. So please check that out. And you can even try with other settings like deleting every connector commencing the exchange and make sure that the server is a FQDN. I hope this will help you. Or if this will not helpful then follow this link:
http://forums.techarena.in/operating...ms/1142831.htm