title: Why not use email address in unsubscribe link
body: <p>Give me few reasons why NOT to include email addresses in plain text form for unsubscribe link that gets sent out in our newsletters.</p>
  
  <p>Right now it's: </p>
  
  <pre><code>xyz.net/unsubscrible?uid=123&amp;email=user@domamin.com
  </code></pre>
  
  <p>I am pushing for: </p>
  
  <pre><code>xyz.net/unsubscrible?uid=123&amp;key=(encrpted_email_md5hash).
  </code></pre>
  
  <p>I don't really like the idea of throwing email addresses in plain text, but need to convince my manager for possible threats.</p>
  
  <p>Update: While all the answers were suggesting how I should secure it and NOT reason why I should secure it, I find do-ob's answer most appropriate.</p>