title: how to enable Magento Customer Account Sharing to global?
body: <p>I am getting the following problem while turning on:</p>
  
  <pre><code>System&gt;Configuration&gt;Default&gt;Customer Configuration&gt;Share Customer Accounts to Global
  </code></pre>
  
  <blockquote>
    <p>"Cannot share customer accounts globally because some customer accounts with the same emails exist on multiple websites and cannot be merged"</p>
  </blockquote>
  
  <p>Why is this problem showing?</p>
  
  <p>Any solution?</p>