title: What is the most efficient way to index email addresses in MySQL?
body: <p>What's the best way to index millions of email addresses in MySQL while minimizing the size of the index?</p>
  
  <p>The index is needed to quickly check whether an email exists in the table. Duplicates are allowed.</p>
  
  <p>Again, the goal is to minimize the size of the index. Currently using a standard index on a varchar field, but considering creating a binary hash and indexing the first few characters. Any other options?</p>