As you may know Azure Information Protection (AIP) provides the capability to define and apply sensitivity labels on documents and emails (when using Outlook client).
Good new, the AIP sensitivity labelling capability is now available also on Outlook Web Access (OWA) – aka Outlook on the Web – and Outlook Mobile.
When you write an email using either of these options, you can then apply the desired AIP sensitivity label; the below screenshots show how to get it from OWA and Outlook Mobile (on Android)
When reading an email with AIP Sensitivity label applied on Outlook Mobile you can identify it with the label applied (bottom of the email), the protection (if any) applied (below the recipient list) and a ‘tag’ icon on top right