I've read many times about putting Exchange into Maintenance Mode before doing an update (or updating the version of .NET as 2016cu2 allows). My question is what exactly does Maintenance Mode do? And does it have any benefit if you are in an environment with just one Exchange server?
Maintenance Mode is generally for clustered Mailbox servers, but it appears to also make changes to the transport queue availability. It stops the mailboxes from becoming active on the server and the DAG support roles from becoming active on the server while in Maintenance Mode. For my one Exchange server I just do the updates. When I had clustered Exchange servers I would use Maintenance Mode.