Eclipse: java.lang.NoClassDefFoundError: javax/activation/DataHandler

I'm trying to send an email in java.Here's the 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());        }

When I compile the project, on line:

Message emailMessage = new MimeMessage(emailSession);

...the following error comes out:

Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataHandler

Note: I'm using java -version: 9.0.4