Indexing your emails with Thunderbird
How it works
The Thunderbird plugin should be installed alongside Tracker. Once installed, the plugin will start indexing your emails when Thunderbird starts, provided Tracker is available. A label in the right of the status bar will inform you of the indexing progress. By default the indexing is throttled to 10 emails/second to limit the CPU/IO activity. This can be changed in the preferences window 3. So far, there is no way to tell the plugin to index only certain folders.
Searching for email
Both tracker-needle (the search GUI) and tracker-search (the command line tool) support searching for emails. However, there is no way to "launch" search results, that is, nothing happens if you double click on a result. To workaround this, you can create a desktop file as explained in this blog post. Such a desktop file might be shipped with later versions of Tracker.