Once you've been migrated to the new Office 365 email service, you have the option of using Microsoft's Outlook App (available for iOS and Android), as opposed to the in-built email app present on mobile devices.
The steps below will assist you in configuring the app for use with your UWA email address.
Navigate to your device's App Store/Play Store, and install the Outlook app:
Open the Outlook App and tap Get Started:
Type in your email address, and tap Continue:
Once the password prompt comes up, change the username field to firstname.lastname@example.org, enter your Pheme password, and tap on Sign in:
Your account is now configured - tap Skip in the bottom left to return to your email: