I too, was experiencing this. There seems to be no indication of a solution anywhere on the web. HOWEVER, I figured it out.
Here's the solution: Strangely, it's not really an exchange issue, but rather an issue with calendaring on the OSX side.
So you understand, here's the configuration that can cause problems:
- you are using an exchange server to connect your email/calendar/notes/tasks...
- You use a PC (or VM PC) for some/most of your exchange/outlook activities
- You may or may not have MS Office 2011 (Mac) installed.
- You have one or more Apple devices connected to your exchange account (iPhone, iPad, any Mac)
After installing Mountain lion, you start noticing events being magically duplicated every few minutes in your outlook draft folder. If you delete an event, another one takes its place.
HERE IS THE FIX:
Short answer: Sync all calendars on all devices
On the apple side (OSX, IOS) you MUST turn on calendar sync in all the exchange accounts on all your devices. I thought I had, then discovered that my MS Office Outlook on my Mac was missing that sync. It doesn't seem to matter which apple device is missing the sync, it only takes one of them. Once you set calendar sync to "on" for all the apple devices that access that calendar, just like magic, the phantom multi event creation stops.
You should check all MS products on the OSX/IOS devices AND all apple devices that allow syncing. I haven't turned on notes sync through the cloud, so that isn't one of the items that cause problems.
If you do this and the multi still appears, you missed something on one of your apple devices.
Sweet!