Hi
I have exchange 2010 Sp1 server .
From Last week, got error when users sending to some particular domain "delayed message/ message not delivered” notification."
When I check Queque viewer I found "451 4.4.0 Primary target IP address respond with "421 Service not available,Closing Transmission channel," Attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts,or delivery failed to all alternate host"
Let me know the solution for this issue.
Thanks in advance