Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
Seald - Keep your conversations secure, everywhere.
Keybase Chat - End-to-end encrypted chat built into Keybase
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
StealthChat - StealthChat is Encrypted, Private, Secure Calls and Chats on Android and Apple iOS
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.