java里如何判断Email是否发送成功？

public boolean send_notify_email(String content, String from, String to, String cc, String bcc, String smtphost, String subject)
throws Exception {
try {
Properties props = System.getProperties();

// Setup mail server
props.put("mail.smtp.host", smtphost);

// Get session
Session session = Session.getInstance(props, null);

// Define message
MimeMessage message = new MimeMessage(session);
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to, false));
message.setRecipients(Message.RecipientType.CC, InternetAddress.parse(cc, false));
message.setRecipients(Message.RecipientType.BCC,InternetAddress.parse(bcc, false));
message.setSubject(subject);
message.setFrom(new InternetAddress(from));
String mailer="servlet";
message.setHeader("X-Mailer", mailer);
message.setSentDate(new Date());
//message.setText(content,"gb2312");
message.setDataHandler(new DataHandler(new servinfo.ByteArrayDataSource(content, "text/html")));
// Send message
Transport.send(message);
return true;
} catch (Exception e) {
ostr = new ByteArrayOutputStream();
e.printStackTrace(new PrintStream(ostr));
return false;
}
}
返回true发送成功，返回false发送失败