With the Private Messenger service, you can exchange secure messages with people you know. Delta Chat is a messaging app that uses email protocols to exchange messages. When used through a Butter Box, people who create accounts on the same Butter Box can send messages to each other without the internet.
Think of the Butter Box like a local post office. Whenever you connect to the Box’s network, your Delta Chat app can send outgoing messages and sync to receive any new ones waiting for you.