I created a very simple Thunderbird plugin that allows tasks in Everdo to be created from mails in Thunderbird. It is pre-alpha quality and there’s no XPI yet. Also, take into account that this is the first Thunderbird plugin I wrote.
Anyway, the code is here:
The main issue now is what to put in the description of a newly created task. Namely, many mails are in HTML format only, and Everdo doesn’t support HTML in the task description.
Apart from that, there’re many other issues, like e.g. missing error checks.