I am unable to send out any external emails from my exchange server 2010 all emails are stuck in queue. I have check my queue viewer and found all emails are stuck there and showing the error as per below.
451 4.4.0 primary target ip address responded with 421 4.2.1 unable to connect
451 4.4 0 primary target ip address responded with attempted failover to alternate host
Please provide me the solution on this. business communication impacting due to this.
THanks in advace