We have two exchange 2010 formed a DAG for HA. And now we want to use third-party POP3 connector to collect incoming emails from oversea servers. In order to have real time fail-over, two POP3 connectors need to support real-time synchorinze their database.
That is, if server A is down, server B is able to auto take over all tasks immediately. And allow us to switch over back to server A manually after the problem fixed.