Delta Chat - free (as in freedom) messaging client that doesn't have their own servers but use existing e-mail server network. All messeges sent by Delta Chat are encrypted. It is good alternative to Messenger, you can write messeges to everyone, who have e-mail.
Read more: https://delta.chat
@ewm thanks, ewm.
For people who care about, support, or build Free, Libre, and Open Source Software (FLOSS).