Central Atomics's Rocketbox integrates with Apple Mail to provide several advanced search-and-retrieval features to OS X's beloved e-mail client.
The product is, first and foremost, a drop-in replacement for Mail's built-in search functionality—upon installation, it overlays the existing search box with a custom one, so that all subsequent searches automatically go through the latter. The company claims that Rocketbox can be up to two hundred times faster than the stock search engine, although building the initial index can take a long time (during which no searches are possible), depending on how many messages are in your inboxes and folders.
Rocketbox also provides as-you-type suggestions in the search box, based on the contents of your search index and of your address book, as well as a convenient preview panel that shows excerpts from the various messages returned from a search.
The application's query engine supports a wide range of wildcards and filters, including restricting searches to specific fields, matching partial strings, and several others.
Rocketbox, which is compatible with both 10.5 and 10.6, costs $15 and can be purchased directly from the company's Website. A 30-day free trial is also available.