In other words use plain vanilla Outlook. A mobile device which syncs directly with the mailbox/calendar via Exchange Active Sync (turn off the device).An application or add-in which syncs your Calendar with an Internet Calendar (such as Google Workspace Sync for Microsoft Outlook).A sync application that directly syncs with your mobile phone.In either case, you should start with disabling all the syncs that have been set up. As said, most duplications appear to be happening when you receive an update for a meeting or when you modify a recurring item see if this is also the case for you. How to locate the source depends a bit on if you are able to reproduce the duplication and how many devices you are synching with.
If not all the items are duplicated, it usually only affects meetings which got updated and recurring items. This can happen in some cases where synching and accessing your mailbox and/or Calendar on multiple mobile devices is involved. How did this happen and how can I troubleshoot and fix this? Looking at my Calendar, I see that several (not all) of my appointments and meetings are suddenly showing up multiple times (some even more than 5 times!).
