Canary Mail offers provider-independent support for PGP on iOS, including for iPhone & iPad.
Canary supports standard PGP that is compatible with all leading tools, apps, and services that support PGP, such as GPGTools, ProtonMail, Tutanota, K-9 Mail, Enigmail, Posteo, etc. Canary's key search is tied into SKS, Keybase, OpenPGP.org & ProtonMail keyservers.
With Canary you can create new PGP keys right on your iPhone or iPad, as well as use and manage all your existing encryption keys. Secret keys are stored securely in encrypted form on your device, and are never sent to server. You can choose to save your key passphrase on device for a limited time, or enter it as needed. In addition, Canary allows you to secure the app with FaceID or TouchID
Canary uses the open source Bouncy Castle encryption library, which supports all modern encryption algorithms.
In addition to the standard PGP encryption mode, Canary offers a fully automated easy-to-use encryption mode for new users that automates key generation and management. This mode is available between Canary users and uses PGP under the hood. You can switch between the Auto and Manual encryption modes at any time, via app Settings.
We are confident that Canary Mail offers the best secure email experience on iOS via its support for PGP / GPG for all your existing email accounts, and its exceptional design and feature set.