[joel20]

Ya esta ya funciona, por si alguien le interesa:

 try
        {

          Properties props = new Properties();
          props.put("mail.smtp.host",host);
          
          Session s = Session.getInstance(props,null);
 
          MimeMessage message = new MimeMessage(s);
 
          InternetAddress fromIA = new InternetAddress(from);
          message.setFrom(fromIA);
 
          message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));                       
          message.setSubject(subject);
          
          MimeMultipart mp = new MimeMultipart();
          mp.setSubType("related");

          //Dividim en dos el mail, mbp1 es el text i mbp2 es l'adjunt
          MimeBodyPart mbp1= new MimeBodyPart();
          mbp1.setText("Aqui possem el text");

          MimeBodyPart mbp2 = new MimeBodyPart();
          FileDataSource fds = new FileDataSource(archivo);
          
          mbp2.setDataHandler(new DataHandler(fds));
      mbp2.setFileName(fds.getName());              
          mp.addBodyPart(mbp1);
      mp.addBodyPart(mbp2); 
          
          message.setContent(mp);
          message.setSentDate(new java.util.Date());
          Transport.send(message);            
     
        }catch (Exception e){
            log("Application ERROR: problem sending an email: "+e.getMessage());
        }