Skype for Slack - Move your slack discussions to a group skype call
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
Calls on Slack - Make voice calls in Slack
Tauria - True end-2-end encrypted group calls for up to 50 people
Pingly - Your communication hub — Email, text & voice in one app
PortaCrypt - Create portable encrypted documents on your Mac