java获取邮箱退信邮件的代码

获取邮箱退信邮件的代码需要使用JavaMail API。以下是一个简单的示例代码，可以从IMAP服务器中获取退信邮件：

import java.util.Properties;
import javax.mail.*;

public class FetchBouncedEmails {
   public static void main(String[] args) throws Exception {

      String host = "imap.gmail.com";
      String username = "youremail@gmail.com";
      String password = "yourpassword";

      // Set the properties for IMAP server
      Properties props = new Properties();
      props.setProperty("mail.store.protocol", "imaps");
      props.setProperty("mail.imap.host", host);
      props.setProperty("mail.imap.port", "993");

      // Get the default Session object
      Session session = Session.getDefaultInstance(props, null);

      // Get the Store object and connect to the IMAP server
      Store store = session.getStore("imaps");
      store.connect(host, username, password);

      // Get the Inbox folder
      Folder inbox = store.getFolder("INBOX");
      inbox.open(Folder.READ_ONLY);

      // Search for messages with the "failure notice" subject
      SearchTerm term = new SubjectTerm("failure notice");
      Message[] messages = inbox.search(term);

      // Print the contents of the messages
      for (int i = 0; i < messages.length; i++) {
         Message message = messages[i];
         System.out.println("Subject: " + message.getSubject());
         System.out.println("From: " + message.getFrom()[0]);
         System.out.println("Text: " + message.getContent().toString());
      }

      // Close the folder and store objects
      inbox.close(false);
      store.close();
   }
}

在上面的代码中，您需要将`host`、`username`和`password`替换为您的实际值。此外，`SubjectTerm`可以替换为其他搜索条件，例如发件人地址或日期。

请注意，此代码仅适用于IMAP服务器。如果您要从POP3服务器中获取退信邮件，则需要使用不同的代码。