java 如何知道发出的邮箱是否签收？是否有回复，代码如何实现？

要知道发出的邮箱是否签收或者是否有回复，需要使用JavaMail API库。具体实现步骤如下：

1. 创建JavaMail Session对象

Properties props = new Properties();
props.put("mail.smtp.host", "smtp.gmail.com");
props.put("mail.smtp.port", "587");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.starttls.enable", "true");

Session session = Session.getInstance(props, new Authenticator() {
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication("YourEmail@gmail.com", "YourPassword");
    }
});

2. 创建邮件对象

MimeMessage message = new MimeMessage(session);

message.setFrom(new InternetAddress("YourEmail@gmail.com"));
message.addRecipient(Message.RecipientType.TO, new InternetAddress("RecipientEmail@gmail.com"));
message.setSubject("Test Email");
message.setText("This is a test email sent from JavaMail API.");

3. 发送邮件

Transport.send(message);

4. 检查邮件状态

要检查邮件状态，需要使用JavaMail API中的POP3协议或IMAP协议。这里以IMAP协议为例。

Store store = session.getStore("imaps");
store.connect("imap.gmail.com", "YourEmail@gmail.com", "YourPassword");

Folder inbox = store.getFolder("INBOX");
inbox.open(Folder.READ_ONLY);

SearchTerm searchTerm = new FromTerm(new InternetAddress("RecipientEmail@gmail.com"));
Message[] messages = inbox.search(searchTerm);

for (Message message : messages) {
    // Check if the message has been read
    boolean isRead = message.isSet(Flags.Flag.SEEN);

    // Check if the message has been replied to
    boolean isReplied = message.isSet(Flags.Flag.ANSWERED);
}

以上代码会连接到Gmail的IMAP服务器，搜索发送给“RecipientEmail@gmail.com”的邮件，并检查邮件是否已读或已回复。请注意，这需要使用JavaMail API 1.5或更高版本，因为它支持IMAP协议的扩展功能。