[cge]

>It also has PGP support (with the help of OpenKeyChain to manage certificates) that works great! There are no other well known solutions for applications supporting PGP in Android; this is huge.

As a caveat here, at least in the non-beta version, support for PGP signatures is intentionally crippled because the original author dislikes them and apparently wants to push encryption (eg, https://github.com/k9mail/k-9/issues/2375), ignoring everyone who points out that this feature may be important or required by policy for them. By default, PGP signatures on unencrypted emails are silently hidden and the emails are displayed as being unsigned. There is no way to sign emails by default, and trying to sign an email results with a popup telling you not to.

[upofadown]

For clarity, the author doesn't like unencrypted but signed emails. Which strikes me as weird but at least it isn't something that people would normally do. They are OK with encrypted and signed emails and presumably encrypted but not signed emails. Here is the rationale:

* https://k9mail.app/2016/11/24/OpenPGP-Considerations-Part-I....

I think there are implementations out there that don't let you send encrypted but unsigned messages (anonymous encrypted). This stuff seems to bring out the enforced opinions in people.