The administrator is trying to release a message from quarantine. The control center returns an error, "Cannot release the message. It has either been released or was unable to contact the SMTP host.";
The message they are trying release remains in quarantine.
In the brightmaillog.log you can see the error:
"Dec 08 2011 06:04:24 [http-41443-Processor7] ERROR - com.brightmail.common.BrightmailException: null ; nested exception is: com.sun.mail.smtp.SMTPSendFailedException: 550 5.7.1 Requested action not taken: message refused"
This error is being returned by the downstream email server. Typically we see this error returned by a Microsoft Exchange server.
This issue can be caused by the messages being released from quarantine being caught as spam or suspected spam by filtering on the Exchange server itself.
This issue is not caused by the Messaging Gateway and a settings change on the downstream email server is needed to resolve the delivery error.