The new Open Source E-Mail Client Mailspring is possible an alternative for your Thunderbird. I am running Linux Debian and there are not so much different mail clients available. Mailspring seems to become more and more interesting.
How to Install Mailspring on Linux Debian
To install mailspring on Linux Deiban first download the latest .deb package from the Download page. To install the client run:
sudo dpkg -i mailspring-*-amd64.deb