Hello I have an Exchange 2010 setup. I noticed just today that I mails have been residing in the queue for long. These were queued mails for yahoo, hotmail, gmail and others.
When I checked the Error I was having :
451 4.4.0 Primary target IP address responded with:
“421 4.4.2 COnnection dropped due to Socket Error.” Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.
Upon a few researches, suggestions were to find out if the server was on a Block List, or to check my DNS.
I have checked my DNS forwarders and everything seems fine. I have also checked out the NAT IP of the mail server at spamhaus.org and its not on their Blocked List too. I have tried to create a custom send connector to those domains and still the queues still persist.