Duplicate Emails? Outlook 2011 for Mac & Exchange Servers

Ben Greiner -

It has come to our attention (twice now) that if a single folder in Microsoft Outlook 2011 has more than 20,000 items there will be problems syncing with a Microsoft Exchange server.  

Once this problem starts, Outlook will begin uploading duplicate messages to Exchange. We have seen folders balloon to over 200,000 items with quadruplicate messages -- essentially bringing Outlook to a halt, exceeding mailbox limits and generally making the affected user feel like their world is crumbling around them.

IMPORTANT - If you use Outlook 2011 and Exchange then login to Outlook Web Access (OWA) and confirm no single folder has anywhere near 20,000 items. Here's how to check:

  1. Highlight each folder. 
  2. In the upper left corner OWA will display the number of items in each folder like this:


You may even want to ensure the inbox does not have any subfolders (if yours does, simply move them outside the Inbox). Outlook works best with smaller inboxes. If you need to reduce the number of items then delete messages or split the folder into multiple folders with a fewer number of messages.


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