User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0 Build ID: 20180910100056 Steps to reproduce: I ran Thunderbird under Windows 10 for the first time in months and upgraded to latest Thunderbird (52.9.1 32-bit). Right-clicking on selected text in messages gave me 'Search Bing for "blah blah"', but Bing has never ever been my search choice. So I went to Tools > Options > General > Default Search Engine to reset to Google. Actual results: My default context menu search switched to Bing. The selection for Default Search Engine has Bing, Yahoo, Amazon, AOL, Twitter, Wikipedia, but no Google. In Thunderbird's about:config editor, I couldn't find Google in any search config variable. Expected results: My Thunderbird default search should not have changed. I should not have lost Google as a choice for Default Search Engine. I've had a Thunderbird profile for decades. http://forums.mozillazine.org/viewtopic.php?f=39&t=3036457 seems like the same problem.

So apparently Google was removed as a search engine provider for Thunderbird in bug 731590 back in 2012. Maybe I'm mis-remembering Thunderbird's behavior, in which case I guess this is INVALID. The workaround is to visit the Google Search for Thunderbird plug-in at https://addons.thunderbird.net/en-US/thunderbird/addon/google-search-for-thunderbi/ in your browser, click [Download Now] and save the .xpi file, in Thunderbird Alt-T to bring up menu, Tools > Add-ons > Extensions, click gearwheel > Install Add-on from File..., navigate to the .xpi you downloaded and Open, confirm the warning and Install, and restart Thunderbird. (You can't install the add-on from within recent Thunderbird because it says "Works with Thunderbird 11.0 - 31.*" .)

(In reply to skierpage from comment #1) > So apparently Google was removed as a search engine provider for Thunderbird > in bug 731590 back in 2012. Indeed. This is being revisited in bug 1427133