Unable to send all Exchange Mail

I have a customer that all there outgoing exchange mail has stopped. I have mixed errors. Some show that I may have been blacklisted and others show I may have been attacked by a virus through the NAT port 25. I get the " You do not have permission to send to this recipient" and domain.com #5.5.0 smtp;550 Mail from (server IP Address) refused. I checked with some blacklist websites and they say I am not listed and the  CBL site says I am. Can anyone make heads or tails. Ran scans on all stations and the server and found no virus's.
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What is your mail domain name? Could you paste the failure report in this page.
gjlawtonAuthor Commented:
I beleive I found the problem late in the night by looking further into the question and help section. It was in the smtp connector. I just was getting 2 different failure notices that were sending me in 2 different directions. I will be setting up a smart host, but after I deleted the smtp connector mail went through the default route and now mail is flowing. Thanks for the response.

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