Telegram PWA provides secure messaging
(All About Windows Phone)

Progressive Web Applications can be quite sophisticated, as we found with Twitter over the last year. Either use them in Edge, via PAWA or sometimes as their own entity in the Store. Telegram, the cross-platform secure messaging service, doesn`t have its own `app` package yet under Windows 10 Mobile, but works very well on the likes of the Lumia 950, which is plenty fast enough in terms of Javascript to handle the encryption/decryption.