Email items missing on a mobile device after synchronization with Exchange ActiveSync

Applies to: Exchange OnlineExchange Server 2016 Enterprise EditionExchange Server 2016 Standard Edition

Symptoms


Consider the following scenario:
 
  • An Exchange ActiveSync (EAS) client is used to receive email items on a mobile device.
  • The EAS client tries to synchronize multiple folders at the same time, or a single folder when the device is being provisioned.
  • There are many new items available for one or more of the folders.

In this scenario, some email items are not available on the mobile device.

Cause


This issue occurs because the Exchange ActiveSync client did not receive the response from a sync request, and Exchange Server did not send the email items in the second request from the client.

Resolution


To resolve this issue, install Cumulative Update 4 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.

Workaround


To work around this issue, disable the synchronization of email items on the EAS client, and then re-enable email items for the client.

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.