NOTE: Encryption is automatically turned on when passcode is set. More information can be found here.
NOTE: Before you begin encryption, the phone must be 80% charged and connected to the charger. All Pixel phones are encrypted by default. So are Nexus 5X, Nexus 6P, and Nexus 9 devices. You can choose to encrypt Nexus 4, Nexus 5, Nexus 7, and Nexus 10 devices. More information can be found here.
When Active Sync is enabled on an existing Exchange account for Windows Phone you will be giving the following prompt:
"Create a new password"
Your phone's security policy has changed, so you'll need to change your lock screen password. Here are the new requirements.
Must have at least 4 digits
Select "Set" to add the password.
If you select "Set" you will be prompted to create a pin."
To verify that the device is encrypted on Windows Phone 8.1, please do the following:
Device encryption is an option that comes disable by default, but you can easily enable the feature using the following steps:
Important Note: A password PIN must be in place to enable the feature if your mobile device doesn't have one when trying to enable Device encryption, you will be automatically redirected to the Sign-in options settings page to create a PIN. Then you would just tap the Add button, under the PIN section, and follow the on-screen wizard to create a new PIN. After the PIN password is created, you can go back to Device encryption settings to verify that the feature has been enabled.
While the feature should work as expected, Windows Phone 8.1 used to display an "encrypted" label in the phone storage settings, and Windows 10 Mobile doesn't provide such visual confirmation in the storage settings. The only way to verify your device is being encrypted is by making sure the "Device encryption" is turned on in the Settings app.
It's important to point out that while encryption is enabled on your mobile device, the operating system and your data stored in the local storage will be encrypted, but device encryption will not encrypt data that you stored on an SD card unless you have build 15007 or later. As such, it's highly recommended that you not save sensitive data on a removable storage, as anyone could easily remove the storage and have unrestricted access to that data from any computer.