Synchronization issues due to folder item count

 
If a folder item count exceeds Microsoft's recommended limits, a user may not have an optimized experience with their mail client/mobile device or could experience errors when synchronizing data to their ActiveSync device. It is possible that a device will continue to synchronize data when these limits are exceeded, but a disruption of service that causes a temporary break in connectivity may cause errors to begin and it may not be possible to restore connectivity, therefore it is highly recommended that these limits not be exceeded.

For Exchange 2007, ActiveSync synchronization issues may occur when folder item counts exceed the following limits:

  • Calendar – 5,000 items
  • Contacts – 5,000 items
  • Deleted items – 20,000 items
  • Inbox – 20,000 items
  • Sent items – 20,000 items
  • Other folders created by user – 50,000
 
 
 
Per Microsoft: ”With a properly architected hardware, an acceptable user experience can still be maintained with item counts as high as 20,000 items (5,000 calendar/contact items). This recommended maximum also depends on the performance capability of your Exchange environment. Your specific hardware choices may result in lower maximum numbers. 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.”
 

For Exchange 2010, ActiveSync synchronization issues may occur when folder item counts exceed the following limits:
  • Calendar – 10,000 items
  • Contacts – 10,000 items
  • Deleted items – 100,000 items
  • Inbox – 100,000 items
  • Sent items – 100,000 items
  • Other folders created by user – 100,000

 

Note: It does not matter how many days worth of e-mail a device is set to synchronize. ActiveSync has to scan the entire folder to determine which messages are within the range specified, so folders that exceed these limits can cause performance issues. 

Max number of folders that can be synchronizied: 1,000

http://technet.microsoft.com/en-us/library/ee832791.aspx

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