Program: 174456
Project: 174456
Buggy source:
public static List<Mail> readMails(Mailbox mailbox,MailFolder mailFolder) throws MessagingException {
  List<Mail> mails=new ArrayList<>();
  Properties props=new Properties();
  props.put("String_Node_Str","String_Node_Str");
  props.put("String_Node_Str","String_Node_Str");
  props.put("String_Node_Str",mailbox.getPop3Port());
  props.put("String_Node_Str",mailbox.getPop3Port());
  props.put("String_Node_Str",mailbox.getPop3Server());
  props.put("String_Node_Str",mailbox.getAccount());
  props.put("String_Node_Str","String_Node_Str");
  Authenticator auth=new Authenticator(){
    @Override protected PasswordAuthentication getPasswordAuthentication(){
      System.out.println(mailbox.getAccount() + "String_Node_Str" + mailbox.getPassword());
      return new PasswordAuthentication(mailbox.getAccount(),mailbox.getPassword());
    }
  }
;
  Session session=Session.getDefaultInstance(props,auth);
  Store store=session.getStore("String_Node_Str");
  store.connect(mailbox.getPop3Server(),mailbox.getAccount(),mailbox.getPassword());
  Folder inbox=store.getFolder("String_Node_Str");
  inbox.open(Folder.READ_ONLY);
  javax.mail.Message[] messages=inbox.getMessages();
  for (  javax.mail.Message message : messages) {
    try {
      Mail mail=new Mail();
      StringBuffer txtBody=new StringBuffer();
      StringBuffer htmlBody=new StringBuffer();
      List<javax.mail.BodyPart> attachments=new ArrayList();
      mail.setFrom("String_Node_Str");
      mail.setTo("String_Node_Str");
      mail.setAttachments(new ArrayList<>());
      Arrays.asList(message.getFrom()).forEach(address -> {
        if (address instanceof InternetAddress) {
          mail.setFrom(mail.getFrom() + ((InternetAddress)address).getPersonal() + "String_Node_Str"+ ((InternetAddress)address).getAddress()+ "String_Node_Str");
        }
 else {
          mail.setFrom(mail.getFrom() + address.toString() + "String_Node_Str");
        }
      }
);
      Arrays.asList(message.getRecipients(javax.mail.Message.RecipientType.TO)).forEach(address -> {
        if (address instanceof InternetAddress) {
          mail.setTo(mail.getTo() + ((InternetAddress)address).getPersonal() + "String_Node_Str"+ ((InternetAddress)address).getAddress()+ "String_Node_Str");
        }
 else {
          mail.setTo(mail.getTo() + address.toString() + "String_Node_Str");
        }
      }
);
      mail.setContentType(message.getContentType());
      Object content=message.getContent();
      if (content instanceof MimeMultipart) {
        parseBodyParts((MimeMultipart)content,txtBody,htmlBody,attachments);
      }
 else {
        getTxtPart((javax.mail.BodyPart)content);
      }
      mail.setTextBody(txtBody.toString());
      mail.setHtmlBody(htmlBody.toString());
      mail.setSubject(message.getSubject());
      mail.setSendDate(message.getSentDate());
      mail.setMailFolder(mailFolder);
      mails.add(mail);
    }
 catch (    IOException e) {
      e.printStackTrace();
    }
  }
  inbox.close(false);
  store.close();
  return mails;
}

Fixed version (ground truth):
public static List<Mail> readMails(Mailbox mailbox,MailFolder mailFolder) throws MessagingException {
  List<Mail> mails=new ArrayList<>();
  Properties props=new Properties();
  props.put("String_Node_Str","String_Node_Str");
  props.put("String_Node_Str","String_Node_Str");
  props.put("String_Node_Str",mailbox.getPop3Port());
  props.put("String_Node_Str",mailbox.getPop3Port());
  props.put("String_Node_Str",mailbox.getPop3Server());
  props.put("String_Node_Str",mailbox.getAccount());
  props.put("String_Node_Str","String_Node_Str");
  Authenticator auth=new Authenticator(){
    @Override protected PasswordAuthentication getPasswordAuthentication(){
      System.out.println(mailbox.getAccount() + "String_Node_Str" + mailbox.getPassword());
      return new PasswordAuthentication(mailbox.getAccount(),mailbox.getPassword());
    }
  }
;
  Session session=Session.getDefaultInstance(props,auth);
  Store store=session.getStore("String_Node_Str");
  store.connect(mailbox.getPop3Server(),mailbox.getAccount(),mailbox.getPassword());
  Folder inbox=store.getFolder("String_Node_Str");
  inbox.open(Folder.READ_ONLY);
  javax.mail.Message[] messages=inbox.getMessages();
  for (  javax.mail.Message message : messages) {
    try {
      Mail mail=new Mail();
      StringBuffer txtBody=new StringBuffer();
      StringBuffer htmlBody=new StringBuffer();
      List<javax.mail.BodyPart> attachments=new ArrayList();
      mail.setFrom("String_Node_Str");
      mail.setTo("String_Node_Str");
      mail.setAttachments(new ArrayList<>());
      Arrays.asList(message.getFrom()).forEach(address -> {
        if (address instanceof InternetAddress) {
          mail.setFrom(mail.getFrom() + ((InternetAddress)address).getPersonal() + "String_Node_Str"+ ((InternetAddress)address).getAddress()+ "String_Node_Str");
        }
 else {
          mail.setFrom(mail.getFrom() + address.toString() + "String_Node_Str");
        }
      }
);
      Arrays.asList(message.getRecipients(javax.mail.Message.RecipientType.TO)).forEach(address -> {
        if (address instanceof InternetAddress) {
          mail.setTo(mail.getTo() + ((InternetAddress)address).getPersonal() + "String_Node_Str"+ ((InternetAddress)address).getAddress()+ "String_Node_Str");
        }
 else {
          mail.setTo(mail.getTo() + address.toString() + "String_Node_Str");
        }
      }
);
      mail.setContentType(message.getContentType());
      Object content=message.getContent();
      if (content instanceof MimeMultipart) {
        parseBodyParts((MimeMultipart)content,txtBody,htmlBody,attachments);
      }
 else {
        if (content instanceof javax.mail.BodyPart) {
          txtBody.append(getTxtPart((javax.mail.BodyPart)content));
        }
 else {
          txtBody.append(content);
        }
      }
      mail.setTextBody(txtBody.toString());
      mail.setHtmlBody(htmlBody.toString());
      mail.setSubject(message.getSubject());
      mail.setSendDate(message.getSentDate());
      mail.setMailFolder(mailFolder);
      mails.add(mail);
    }
 catch (    IOException e) {
      e.printStackTrace();
    }
  }
  inbox.close(false);
  store.close();
  return mails;
}