Delta Chat is like Telegram or Whatsapp but without the tracking or central control. Delta Chat does not need your phone number. Uses the most massive and diverse open messaging system ever: the existing e-mail server network. Chat with anyone if you know their e-mail address, no need for them to install DeltaChat! All you need is a standard e-mail account. Full clients for multiple platforms available.

Github: https://github.com/deltachat/