We just recovered yesterday from an Exchange database failure. Database was restored and most mail seems to be flowing in and out except for mail sent to a few domains. We have a 2-node DAG (EXCH01 and EXCH02) with the database currently active on EXCH01. All mail flows thru a Barracuda Spam 300 firewall and up until the recovery yesterday all the email flowed fine in both directions. Barracuda has not been touched. Delivery to a few domains is showing as delayed in the queue and is bouncing back with the message:
Diagnostic information for administrators:
Generating server: EXCH01.neweraopt.com
Receiving server: edge.receivingdomain.com (xxx.xx.xx.xxx)
Remote Server at edge.receivingdomain.com (xxx.xx.xx.xxx) returned '400 4.4.7 Message delayed'
11/13/2017 8:29:42 PM - Remote Server at edge.receivingdomain.com (xxx.xx.xx.xxx) returned '451-4.4.0 Primary target IP address responded with: "554-edge2.receivingdomain.com 451 4.4.0 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts. The last endpoint attempted was xxx.xx.xxx.xxx:25'
I have checked out MX records and they seem fine. I have also checked several blacklist sites and our domain is not listed.
If any additional info is needed please let me know. Thank you.