I've got an email message flow issue. Most of the messages in the email queue have the error: Last error 421 4.4.2 connection dropped due to connection reset
In my research within my company, I found that the MX records and A records for the email servers had disappeared from DNS on our main DC so they have been added back in and DNS flushed and reregistered. That doesn't seem to have helped.
We are using MS Forefront as our AV, the server is configured with Windows 2008 R2 and Exchange 2010. This is an Exchange cluster.
I haven't checked our firewall or router. DNS has been fixed on our DC and replication has been forced so hopefully it's replicated through our domain.
I know there are similar questions posted on EE but none of the fixes I found pertained or they didn't work for me.
Any help would be greatly appreciated as I have many emails stuck in my queues.