You have other alternatives such as Bitmessage
https://bitmessage.org/wiki/Main_Page
https://scottlinux.com/2013/07/26/bitmessage-how-to-for-debian-and-ubuntu-linux/
https://bitmessage.ch/
Bitmessage Mail Gateway
With the Tor Network
Email and Messaging
http://sigaintevyh2rzvw.onion/
http://bitmailendavkbec.onion – swiss email
http://365u4txyqfy72nul.onion/ – Anonymous E-mail sevice. You can only
communicate with other users currently using this service. So tell all your
friends about it!
http://sms4tor3vcr2geip.onion/ – SMS4TOR – Self destructing messages
http://notestjxctkwbk6z.onion/ – NoteBin – Create encrypted
self-destructing notes
http://torbox3uiot6wchz.onion/ – [TorBox] The Tor Mail Box
http://u6lyst27lmelm6oy.onion/index.php – Blue matrix chat NOT UP ALL THE
TIME so chek often to see when it is
http://wi7qkxyrdpu5cmvr.onion/ – Autistici/Inventati
http://u4uoz3aphqbdc754.onion/ – Hell Online
