Emails are not being sent from our server running SBS 2008 Standard, Exchangs is configured to send and receive mail and has been working fine for the last couple of weeks. The server was rebooted and now emails sit in the queue. However, emails are being received fine. We use a smart host and they say that they cannot see the server connecting to them at all.
The error is: 451 4.4.0 primary target IP address responded with ". " attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts, or delivery failed to all alternate hosts.