Why is Windows Explorer making external connections?

This is normal and expected behavior for windows system. The IP you mentioned resolves to sinwns2012412.wns.windows.com.

The Windows Push Notification Services (WNS) enables third-party developers to send toast, tile, badge, and raw updates from their own cloud service. This provides a mechanism to deliver new updates to your users in a power-efficient and dependable way.

How it works: The following diagram shows the complete data flow involved in sending a push notification. It involves these steps:

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  1. Your app sends a request for a push notification channel to the Notification Client Platform.

  2. The Notification Client Platform asks WNS to create a notification channel. This channel is returned to the calling device in the form of a Uniform Resource Identifier (URI).

  3. The notification channel URI is returned by Windows to your app.

  4. Your app sends the URI to your own cloud service. This callback mechanism is an interface between your own app and your own service. It is your responsibility to implement this callback with safe and secure web standards.

  5. When your cloud service has an update to send, it notifies WNS using the channel URI. This is done by issuing an HTTP POST request, including the notification payload, over Secure Sockets Layer (SSL). This step requires authentication.

  6. WNS receives the request and routes the notification to the appropriate device.

Reference: https://msdn.microsoft.com/en-us/library/windows/apps/hh913756.aspx

I had the same situation today. I have stopped and disabled the service


and the connection does not came up anymore.