Outlook 2011/2016 and Exchange Server - High Item Count

Ben Greiner -

JAN 2017 UPDATE: Although Outlook 2016 for Mac is more robust and able to handle a larger quantity of messages than the tired old 2011 version, it's still not the best email client when it comes to large databases (over 10GB). We have seen a direct relationship between the size of an Outlook database and the Spinning Wheel of Death. It typically breaks down like this:

  • Up to 5GB = No Issues
  • 5 to 10GB = Occasional Issues
  • Over 10GB = Issues!



  • Keep each folder to under 5,000 items. Due to the Mac OS journaled drives, this can help speed up those folder load times.

  • No more than 30 subfolders to any any 1 folder, including the Inbox. The Exchange connection cycles the updates for each top level folder and can timeout if there are too many that it needs to pickup under that top level.

  • 500 folders should be the max. It sounds like a lot, but they can add up quickly when nesting folders in other folders.

  • Divide the mail up by year, by quarter, or even by month if you have that much mail.

  • Folder creation and movement is best done via webmail.

  • Moving large amounts of mail messages (not folders) can be done in Outlook. However, do NOT attempt to move more than one clump of mail at a time. Make a move and WAIT until it completes before moving more mail. This can be a slow and tedious process, but the performance benefits are worth it!



The Outlook 2011 for Mac Exchange client is clearly not as good as its Windows equivalent. However, it's the best Outlook client Mac users have ever received from Microsoft so we can't complain too much! Below are tips to improve your Outlook 2011 experience, some taken directly from Microsoft's support site.

You can help avoid poor performance in Outlook by carefully managing the number of items in folders, especially the Outlook folders that are heavily used. These folders include Inbox, Calendar, Tasks, Sent Items, and Deleted Items, with a special emphasis on Inbox, Sent Items, and Deleted Items as these are the first to be downloaded. This applies to any other personal folders that are heavily used.

The recommended number of items in a folder depends on several factors. These factors include the client’s proximity to the server, the storage infrastructure, the load on the hard disks (client and server), the number of users, and the number of restricted views.

Microsoft recommends that you maintain a range of 2,500 to 5,000 items in a folder. Additionally, you can create more top-level folders or create subfolders under Inbox, Sent Items, and Deleted Items. The Outlook performance costs that are associated with index creation are greatly reduced when working within folders with 5000 items or less.

The following list includes ways that you can help manage the number of items in folders:

  • Use folder hierarchies to help keep the number of items in a folder to the recommended values. We recommend that you use no more than three levels of folders. For example, the Inbox is the top level. Then you have a subfolder labeled "2010" for all email messages that were received in 2010. And then you have a subfolder inside of the 2010 folder named "January" for the January email messages. This folder named January is the third level.
  • Use server-based archiving solutions.
  • Use mailbox size limits.



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