Microsoft Exchange Server is a mail server, calendaring software, and contact manager. It runs on Windows Server and is part of the Microsoft Servers line of products. The improvements made in Exchange 2019 have made it easier to load balance Exchange-related traffic.

Exchange 2019 includes the following solutions for switchover and failover redundancy:

  • High availability: Exchange 2019 uses Database Availability Groups (DAGs) to keep multiple copies of your mailboxes on different servers synchronized. That way, if a mailbox database fails on one server, users can connect to a synchronized copy of the database on another server.
  • Site resilience: You can deploy two active directory sites in separate geographic locations, keep the mailbox data synchronized between the two, and have one of the sites take on the entire load if the other fails.
  • Online mailbox moves: During an online mailbox move, email accounts are still accessible. Users are only locked out for a brief period of time at the end of the process when the final synchronization occurs. Online mailbox moves can be performed across forests or in the same forest.
  • Shadow redundancy: Shadow redundancy protects the availability and recoverability of messages while they are in transit. With shadow redundancy, the deletion of a message from the transport databases is delayed until the transport server verifies that all the next hops for that message are completed. If any of the next hops fail before reporting successful delivery, the message is resubmitted for delivery to the hop that did not complete.