I have exchange server 2010 and we have set mail relay to logix. Means, our exchange send email to Logix and then logix forward email to repient domain. But today our exchange is not connecting with logix. earlier IP reputation was poor, so I changed the IP of exchange and same NAT in firewall. OWA is working fine using IP and DNS name. Again, I set relay to LOGIX, it is not connecting with exchange.
451 4.4.0 Primary target IP responded with: "421 4.4.2 connection drop due to socket error. "attemped failover to alternate host but that did not succeed. Either there are no alternate host or delivery failed to alternate host."