My other favorite is when corporate comms or HR sends out some calendar invite to a massive number of people, does not use bcc, and then the server crashes when

My other favorite is when corporate comms or HR sends out some calendar invite to a massive number of people, does not use bcc, and then the server crashes when folks go in to the accepted invite on their calendar and you get thousands of calls to 'check availability' flood in. Have seen that bring the Exchange Server to its knees a few times :)