of synchronous and asynchronous sends has
 been performed. The application is not required to wait for an asynchronous send to complete before sending the next
 message.

 <p>
 <b>Close, commit or rollback</b>: If the <tt>close</tt> method is called on the <tt>MessageProducer</tt> or its
 <tt>Session</tt> or <tt>Connection</tt> then the Jakarta Messaging provider must block until any incomplete send operations have
 been completed and all <code>CompletionListener</code> callbacks have returned before closin