The newest Thunderbird for Mint 18 and Ubuntu 16.04

Some reason the newest Thunderbird is not available in Mint 18 and Ubuntu 16.04, so the solution is to install Ubuntuzilla’s version.

https://sourceforge.net/p/ubuntuzilla/wiki/Main_Page/#installation

echo -e "\ndeb http://downloads.sourceforge.net/project/ubuntuzilla/mozilla/apt all main" | sudo tee -a /etc/apt/sources.list > /dev/null

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 2667CA5C

sudo apt-get update

sudo apt-get install thunderbird-mozilla-build