Do you struggle to keep tabs on your Thunderbird inbox? The SIMILE Seek extension might be the answer to your problems. The extension adds faceted browsing to Thunderbird, which allows you to search and manage your email messages in a radically different way than you are used to.
To better understand how faceted browsing works, take a look at sites like the venerable Open Directory Project. The site allows you to narrow your search by filtering the data by the criteria, or facets, you choose. For example, you may start with a broad category called Computer, then narrow it to Open Source, then Software, and so on. Each time you choose a category, you effectively add a facet to your search, and thus make it more precise.