The Notifier cannot reach the device with the tracked IP address.
Some or all devices cannot be addressed directly because they are private relative to the MobiLink server. For example, a remote device is on a private sub-network and its address is internal to that network.
Try one of the following:
If the IP address is assigned by a public wireless carrier or ISP, you may be able to upgrade your carrier plan so that you can obtain public IP addresses instead of private ones.
If you are using Wi-Fi, the IP security policy in your organization may stop your device from being reachable. Contact your IT department for assistance.
Use an SMTP gateway.
If the device's IP address is never reachable, you may want to stop device tracking on the Listener with the -g option. The -g option is useful when you do not want to use device tracking but you do want delivery confirmation. If you are using delivery confirmation, the first attempt to connect will be via UDP, and the lack of confirmation will prevent further UDP attempts.
For more information about delivery confirmation, see confirmation_handler property.