The EWS sends a heartbeat signal to the ENS every 15 minutes.
The following figure describes the ENS resubscription process flow. If the ENS2 does not receive a status update from the EWS, the ENS2 can send the Boxer a silent push notification to check in with the EWS. In addition, the ENS2 is listening for status updates from the EWS. To keep these subscriptions alive, the Boxer application has a check-in mechanism which validates if an EWS subscription is alive. The EWS sends notification updates to the Boxer until the EWS subscription is active and alive. The Exchange can drop the EWS push subscriptions which are triggered by the Exchange and the ENS does not have control over the subscription lifetime. The subscriptions have limited lifetime due to the movement of mailbox, throttling, and so on. The EWS is responsible for informing the ENS when there is a change in a user's mailbox. The Boxer application initiates these subscriptions with the ENS and the ENS subscribes a user's account with the EWS. The ENS2 uses the Exchange Web Services (EWS) subscription to notify the Boxer application of any changes in an end-users mailbox, including the email notifications. ENS2 Resubscription and Badge Count Accuracy Limitations This topic lists the various troubleshooting procedures for ENS.
