Seems to me the most secure messengers are probably those that don't make a big deal about it. One of the most intriguing secure messengers, in my opinion, is S

Seems to me the most secure messengers are probably those that don't make a big deal about it. One of the most intriguing secure messengers, in my opinion, is Semaphor -- https://spideroak.com/semaphor/ https://spideroak.com/semaphor/ -- and they publish the encryption code for inspection and analysis (though not the keys, obviously).