I thought that Thunderbird (along with Firefox) was based on the Mozilla application suite which itself was open sourced from the code that Netscape wrote for

I thought that Thunderbird (along with Firefox) was based on the Mozilla application suite which itself was open sourced from the code that Netscape wrote for their browser, mail and news client, and html composer/editor aka Netscape Communicator. I still use Firefox as my main browser, and Thunderbird as my mail and news client and have been using their earlier incarnations since the Netscape days.