For a long time, I've sent messages to specific domains remain in the queue. I have done several things and yet nothing. Just as there is a domain that we send but not receive him. I keep getting the following errors:
"451 4.4.0 Primary target IP address respond with: "421 4.4.2 Connection dropped due to ConnectionReset."" Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts."
I thank them if you can help me. I'm using Exchange 2010.