title: How can an e-mail database be structured so as to facilitate multi-dimensional search, such as by sender, by receiver, by subject and by time?
body: <p>e-mail database is a database that stores a large number of electronic mail messages. It can be viewed as a semi structured database consisting mainly of text data. </p>
  
  <p>How can such an e-mail database be structured so as to facilitate multi-dimensional search, such as by sender, by receiver, by subject and by time?</p>