Rated 4 out of 5 stars
It works on Thunderbird 68.5.0 (in opening emails in a new tab). Thanks Dugite-Code for helping :)This review is for a previous version of the add-on (2.0.2).
There is currently a known bug where if your emails open in a new window lookout will not run. Please try switching to opening emails in a new tab, if your problem persists please open an issue on github.