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Why does my IOS Folder Stop Syncing Automatically or Ping Sync Loop

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There is a problem that comes up in Exchange from time to time that will cause Direct Push to stop working on that device for a particular folder. The issue happens when Exchange sends out an update notification to the IOS device, the IOS device then issues a Sync command, and then Exchange responds with no data. If this happens 5 times, the IOS device will mark that folder as "Blacklisted" and will no longer automatically sync that folder until a manual sync is performed. If this happens to a non critical folder, the issue may never be noticed and will eventually work itself out when the item causing the problem is no longer in the sync window ( the number of days you have configured your device to keep items ). However, if this happens to a critical folder ( inbox ) it is noticed immediately and will usually result in a call to the helpdesk.

There are 5 methods to alleviate this behavior. 1. Change the “sync Window”. The sync window is the number of days of mail that is configured to be stored on the device. If we reduce the size ( sync fewer days ) of this window and the item that has the issue is no longer in the sync window, there will be no issue. 2. Change the device syncing method from “push” to “fetch”. 3. Move the affected item to another folder and/or delete old items in an effort to get the affected item out of the sync window. It will require Microsoft support intervention to track down the specific item, but hopefully cleaning up the inbox will result in success. 4. Delete the affected item, this will also require Microsoft support to identify the specific item.

Here is a help desk template one of my customers asked me to create. I thought I would share it for all.

When a client first calls in with this issue, you have the choice of reducing the sync window or changing the sync method. How you proceed should be discussed with the affected client. Changing to fetch mode eliminates the issue, but the device will only update on a 15 minute schedule.
1. Change to “fetch” mode:
 a. Open “settings” on the IOS device and select “mail, contact, and calendars”
 b. Select “fetch new data” and move the slider on the “Push” line to off.
 c. Scroll down and make sure the schedule checked is “Every 15 minutes”.

2. Change the sync window to 1 day while also cleaning up the inbox.
 a. Open “settings” on the IOS device and select “mail, contact, and calendars”
 b. Select the affected email account
 c. Scroll down and select “Mail Days to Sync” and check “1 Day”. If the items causing the issue was from today, they will have to wait 24 hours to see if this resolved the issue. They will need to manually update the mailbox for that 1 day. After 24 hours, the item should be out of the sync windows of 1 day and should update automatically thereafter. You can gradually increase the sync windows as time goes by keeping the affected item out of the sync window.  

3. If option 2 fails and 24 hours later we still have the issue, we need to perform a more invasive and complex procedure (this is not usually required).
 a. Remote into the affected user’s desktop that has Outlook installed.
 b. Download MFCMAPI from https://mfcmapi.codeplex.com/ and extract the file to the desktop (does not require installation).
 c. Log into Outlook, and change “Account Setting” to online mode.
 d. Remove the account from the mobile device.
 e. Log into the user’s OWA, go to settings, and remove the affected device from the mobile device list.
 f. Execute MFCMAPI and open the user’s mailbox:
  A. Open Mailbox with MFCMAPI while Outlook profile is set to online mode. Run this from the clients desktop.
  B. Session --> Logon -->Root Container
  C. Remove all folders that start with Airsync
 g. Change the sync window on the device to 1 day ( see action item 1).
 h. Re-create the device partnership.

4. If option 1 is unacceptable and option 2 and 3 fail. Open a case with Microsoft to find the affected item and remove it from the mailbox.

There are some other things that can be done on an org wide level to reduce the frequency of this happening (though it is not a common issue).
1. Follow calendar best practices as discussed here: https://support.office.microsoft.com/en-us/article/Best-practices-when-using-the-Outlook-Calendar-d93f72d3-2361-4e0d-8d6a-5c4939c17f39?CorrelationId=87beb498-f681-4e70-a137-b0b002d76d02\&ui=en-US\&rs=en-US\&ad=US . Pay SPECIAL ATTENTION to having zero events with a never ending date. This is the most coming reason why changing the sync window to 1 day fails because a never ending event always needs to be sync’d.
2. Limit the number of items stored in the mailbox. Although this is fairly rare, Having 10’s of thousands of items in the inbox with a large sync window, increases the chance of having an issue.
3. Reduce the sync window size as a best practice.