title: SES error missing final '@domain'
body: <p>I'm using python lib <code>boto</code> for sending emails via SES. And when I tried to send to more than 30 (but less than 50, so limit is not exceeded) recipients, I got an error:</p>
  
  <pre><code>  &lt;Error&gt;
      &lt;Type&gt;Sender&lt;/Type&gt;
      &lt;Code&gt;InvalidParameterValue&lt;/Code&gt;
      &lt;Message&gt;Missing final '@domain'&lt;/Message&gt;
    &lt;/Error&gt;
  </code></pre>
  
  <p>My <code>to_addresses</code> is empty list, all recipients are in <code>bcc_addresses</code> list.</p>
  
  <p>What does it mean? Every recipient's address is valid and sender address is verified and valid.</p>