title: Eclipse: java.lang.NoClassDefFoundError: javax/activation/DataHandler
body: <p>I'm trying to send an email in java.
  Here's the code:</p>
  
  <pre><code>String mailSmtpHost = "smtp.example.com";
  String mailTo = "email@example.com";
          String mailFrom = "email@example.com";
          String mailSubject = "Email subject";
          String mailText = "Some text";
          Properties properties = new Properties();
          properties.put("mail.smtp.host", mailSmtpHost);
          Session emailSession = Session.getDefaultInstance(properties);
  try {
              Message emailMessage = new MimeMessage(emailSession);
              emailMessage.addRecipient(Message.RecipientType.TO, new InternetAddress(mailTo));
              emailMessage.setFrom(new InternetAddress(mailFrom));
              emailMessage.setSubject(mailSubject);
              emailMessage.setText(mailText);
              emailSession.setDebug(true);
              Transport.send(emailMessage);
          }catch(Exception e) {
              System.out.println("Errore email: "+e.toString());
          }
  </code></pre>
  
  <p>When I compile the project, on line:</p>
  
  <pre><code>Message emailMessage = new MimeMessage(emailSession);
  </code></pre>
  
  <p>...the following error comes out:</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataHandler
  </code></pre>
  
  <p>Note: I'm using <code>java -version: 9.0.4</code></p>