Java EE (Java Enterprise Edition) General Discussion

Hi,
I want to use javamail to backup my email account and save it in eml format. but my programme always throw an error: "error loading POP3 headers" when it has saved several mails. the code may have some problems. What is the reason and how to resolve the problem? The follow code is my programme:
public void loadMailListFromServer() {
Properties props = System.getProperties();
props.setProperty("mail.store.protocol", "pop3");
props.setProperty("mail.pop3.host", "pop.qq.com");
props.setProperty("mail.pop3.port", "995");
props.setProperty("mail.pop3.ssl.enable", "true");
props.put("mail.debug", "false");
Session session = Session.getDefaultInstance(props, new Authenticator(){
public PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("166505261@qq.com", "MY_PASSWORD");
}
});

try {  
Store store = session.getStore("pop3");   
store.connect();   
Folder folder   = store.getFolder("INBOX");  
folder.open(Folder.READ\_ONLY);  
int total = folder.getMessageCount();  
for(int i=1; i\<=total; i++) {  
 try {  
 MimeMessage msg = (MimeMessage)folder.getMessage(i);  
 loadMail(session, i, msg);  
 } catch(Exception e) {  
 e.printStackTrace();  
 System.out.println("exception and reset...");  
 if(!store.isConnected()) {  
 store.close();  
 }  
 if(folder.isOpen()) folder.close();  
 store = session.getStore("pop3");  
 store.connect();  
 folder = store.getFolder("INBOX");  
 folder.open(Folder.READ\_ONLY);  
 total = folder.getMessageCount();  
 i--;  
 }  
}  
store.close();  
} catch(Exception e) {  
 e.printStackTrace();  
}  

}
protected void loadMail(Session session, int messageNo, MimeMessage message) throws Exception {

SimpleDateFormat sdtf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

String subject = message.getSubject();
Date recvDate = message.getSentDate();
String messageId = message.getMessageID();

String uid = UUID.randomUUID().toString();
File dir = new File("D:/mail_backup/");
File file = new File(String.format("D:/mail_backup/%s.eml", uid));
if(!dir.exists()) dir.mkdirs();
if(!file.exists()) dir.createNewFile();
OutputStream ips = new FileOutputStream(file);
message.writeTo(ips);
ips.close();
System.out.println(sdtf.format(recvDate) + " mail subject："
+ subject + "|messageID="+ messageId);
}