Security, How to encrypt Windows Mobile devices
This page provides instructions on how to encrypt a Windows Mobile device.
WARNING: When encrypting a device, it is imperative that you remember the password/PIN used to encrypt the device. If you forget the password/PIN, all data on the device will be lost.
Follow instructions provided by Windowscentral.com: http://www.windowscentral.com/how-enable-device-encryption-windows-10-mobile
Furthermore, you need to be careful when to choose to enable this feature, as it's possible that encrypting your device may cause some issues, such as problems with emails not synchronizing with your phone.