Deltachat is opensource for every platform it supports: https://github.com/deltachat https://github.com/deltachat It also includes a core library in C: https:/

Deltachat is opensource for every platform it supports: https://github.com/deltachat https://github.com/deltachat It also includes a core library in C: https://github.com/deltachat/deltachat-core https://github.com/deltachat/deltachat-core The spec is documented here: https://github.com/deltachat/spec/blob/master/spec.md https://github.com/deltachat/spec/blob/master/spec.md