Today we had an issue where a Mailbox server did not fail over to our secondary or tertiary domain controllers. Basically, what this does is it stops that server from providing the cluster the status of that database. This caused the inability for users on those databases to connect. We have made changes to the domain controller logic within Exchange to reduce the possibility of a reoccurrence. In addition, since certain databases were dismounted, the transport would not accept mail, so this would cause a bottle neck in mail delivery for folks on LOUIE.
As always please remember that during these times you have https://admin.exchangedefender.com/livearchive.php at your fingertips to ensure that your clients continue to transact business. Remember with ExchangeDefender they are never down.