Java Security

I write a program that encrypt an email with text content and attached file.
When the email is received:
- On MS Outlood 2003: There's no content in the email and have no ecrypted sign.
- On Thunder bird version 2.0 : I can see the content and the attachment file but still have no ecrypted sign in the email. (Note: if i send this mail to user that have no trusted certificate installed than he can't read the email).
Anybody can help me what's going wrong ?
Here 's my program:

MailCrypto mailCrypto=new MailCrypto();
MimeBodyPart bp=new MimeBodyPart();
bp.setHeader("Content-Type", "text/plain");
bp.setContent("Hello World!!!", "text/plain; charset=\"ISO-8859-1\"");

MimeBodyPart bp2=new MimeBodyPart();
FileDataSource fileAttachment = new FileDataSource("C:\\csb.log");
DataHandler dh = new DataHandler(fileAttachment);
bp2.setDataHandler(dh);
//bp2.setDisposition(Message.ATTACHMENT);
bp2.setFileName(fileAttachment.getName());
bp2.setHeader("Content-Type", "application/log");

KeyStore credentials=getKeyStore("123456","C:\\keystore_viettq.p12");
Certificate[]   chain = credentials.getCertificateChain("mycert");
X509Certificate cert = (X509Certificate)chain[0];
	
// set up the generator
SMIMEEnvelopedGenerator  gen = new SMIMEEnvelopedGenerator();
          
gen.addKeyTransRecipient(cert);

//--- Create Base Message

MimeMessage baseMsg=new MimeMessage((Session)null);
Multipart multipart = new MimeMultipart();
multipart.addBodyPart(bp1);
multipart.addBodyPart(bp2);

Address fromUser = new InternetAddress("\"Trinh Quang Viet\"<trinh.quang.viet@vsi-international.com>");
Address toUser = new InternetAddress("trinh.quang.viet@vsi-international.com");

baseMsg.setHeader("Content-Type", "multipart/mixed");
baseMsg.setFrom(fromUser);
baseMsg.setRecipient(Message.RecipientType.TO, toUser);
baseMsg.setSubject("Example Encrypted Message");
baseMsg.setContent(multipart);
baseMsg.saveChanges();

//---End Test part

// generate the enveloped message
MimeBodyPart encryptedPart = gen.generate(baseMsg, SMIMEEnvelopedGenerator.RC2_CBC, "BC");
Multipart finalMutiPart = new MimeMultipart();
finalMutiPart.addBodyPart(encryptedPart);

Properties props = new Properties();
props.put("mail.smtp.host", "mail.vsi-international.com");
props.put("mail.smtp.auth", "true");
props.put("mail.debug", "true");
props.put("mail.smtp.user", "trinh.quang.viet@vsi-international.com");
props.put("mail.smtp.password", "xxxxxxxx");
props.put("mail.smtp.port", "25");

Authenticator auth = new SMTPAuthenticator();
Session session = Session.getDefaultInstance(props, auth);
session.setDebug(true);
MimeMessage theEMail = new MimeMessage(session);
//theEMail.setHeader("Content-Type", "application/x-pkcs7-mime");
theEMail.setHeader("Content-Type", "multipart/mixed");
theEMail.setFrom(fromUser);
theEMail.setRecipient(Message.RecipientType.TO, toUser);
theEMail.setSubject("Example Encrypted Message");
theEMail.setContent(finalMutiPart);
theEMail.saveChanges();
Transport.send(theEmail);

Thanks