Sorting, searching, and making sense through thousands of e-mails can be very messy. Even if powerful e-mail clients today like GMail and Outlook can handle being your conversation assistant, you still end up spending more time searching past e-mails to get the full picture of your conversations. Of course this is a problem of good old keyword search. While search technology has gone through a lot, people believe that semantic search is the next step. One tool that exemplifies this is Meshin.
http://www.makeuseof.com/dir/meshin-semantic-search-engine-for-email/