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:
- Highlight each folder.
- 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.
Related Articles of Interest
- Messages in sent items constantly being re-uploaded - Outlook for Mac - Microsoft Answers
- Outlook 2011 mailboxes are duplicating many users messages
- Understanding the Performance Impact of High Item Counts and Restricted Views: Exchange 2007 Help
QUOTE FROM MICROSOFT LIBRARY:
Ideally, it is best to keep the Inbox and Sent Items folders less than 20,000 items, and the Contacts and Calendar item counts less than 5,000.