JavaMail抄送功能问题及解决方案

在使用JavaMail库发送带有抄送功能的邮件时，有时会遇到抄送人无法收到邮件的情况。这通常是由于配置不当或邮件服务器限制引起的。本文将详细介绍如何正确配置JavaMail，确保抄送功能正常运行。

首先，确保你的项目中包含了必要的JavaMail依赖。在Maven项目中，需要在pom.xml文件中添加如下依赖：

    com.sun.mail
    javax.mail
    1.5.6


    com.sun.mail
    smtp
    1.5.2

接下来，我们来看一个简单的JavaMail服务类，该类用于发送包含抄送功能的邮件：

package com.ssm.boot.service;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;

public class MailService {
    private static final Logger logger = LoggerFactory.getLogger(MailService.class);
    private static final String DEFAULT_SENDER_NAME = "your-email@example.com";
    private static final String DEFAULT_SENDER_PASS = "your-password";
    private static final String DEFAULT_SMTP_HOST = "smtp.example.com";

    private String smtpHost;
    private String sendUserName;
    private String sendUserPass;
    private MimeMessage mimeMsg;
    private Session session;
    private Properties props;
    private Multipart multipart;
    private List attachments = new LinkedList<>();

    public MailService(String smtpHost, String sendUserName, String sendUserPass, String to, String cc, String subject, String body, List attachments) {
        this.smtpHost = smtpHost;
        this.sendUserName = sendUserName;
        this.sendUserPass = sendUserPass;
        init();
        setFrom(sendUserName);
        setTo(to);
        setCc(cc);
        setSubject(subject);
        setBody(body);
        if (attachments != null) {
            for (String attachment : attachments) {
                addAttachment(attachment);
            }
        }
    }

    private void init() {
        if (props == null) {
            props = System.getProperties();
        }
        props.put("mail.smtp.host", smtpHost);
        props.put("mail.smtp.auth", "true");
        session = Session.getDefaultInstance(props, null);
        session.setDebug(true);
        mimeMsg = new MimeMessage(session);
        multipart = new MimeMultipart();
    }

    public static MailService create(String smtpHost, String sendUserName, String sendUserPass, String to, String cc, String subject, String body, List attachments) {
        return new MailService(smtpHost, sendUserName, sendUserPass, to, cc, subject, body, attachments);
    }

    public static MailService createDefault(String to, String cc, String subject, String body, List attachments) {
        return new MailService(DEFAULT_SMTP_HOST, DEFAULT_SENDER_NAME, DEFAULT_SENDER_PASS, to, cc, subject, body, attachments);
    }

    private boolean setSubject(String subject) {
        try {
            mimeMsg.setSubject(subject);
        } catch (MessagingException e) {
            logger.error("Failed to set subject: ", e);
            return false;
        }
        return true;
    }

    private boolean setBody(String body) {
        try {
            BodyPart bodyPart = new MimeBodyPart();
            bodyPart.setContent(body, "text/html;charset=UTF-8");
            multipart.addBodyPart(bodyPart);
        } catch (MessagingException e) {
            logger.error("Failed to set body: ", e);
            return false;
        }
        return true;
    }

    private boolean addAttachment(String filename) {
        try {
            if (filename != null && !filename.isEmpty()) {
                BodyPart bodyPart = new MimeBodyPart();
                FileDataSource fileDataSource = new FileDataSource(filename);
                bodyPart.setDataHandler(new DataHandler(fileDataSource));
                bodyPart.setFileName(MimeUtility.encodeText(fileDataSource.getName(), "utf-8", null));
                multipart.addBodyPart(bodyPart);
                attachments.add(filename);
            }
        } catch (Exception e) {
            logger.error("Failed to add attachment: ", e);
            return false;
        }
        return true;
    }

    private boolean setFrom(String from) {
        try {
            mimeMsg.setFrom(new InternetAddress(from));
        } catch (MessagingException e) {
            logger.error("Failed to set from address: ", e);
            return false;
        }
        return true;
    }

    private boolean setTo(String to) {
        if (to == null) return false;
        try {
            mimeMsg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
        } catch (MessagingException e) {
            logger.error("Failed to set to address: ", e);
            return false;
        }
        return true;
    }

    private boolean setCc(String cc) {
        if (cc == null) return false;
        try {
            mimeMsg.setRecipients(Message.RecipientType.CC, InternetAddress.parse(cc));
        } catch (MessagingException e) {
            logger.error("Failed to set cc address: ", e);
            return false;
        }
        return true;
    }

    public boolean send() {
        try {
            mimeMsg.setContent(multipart);
            mimeMsg.saveChanges();
            Transport transport = session.getTransport("smtp");
            transport.connect(smtpHost, sendUserName, sendUserPass);
            transport.sendMessage(mimeMsg, mimeMsg.getAllRecipients());
            transport.close();
            logger.info("Email sent successfully.");
            return true;
        } catch (Exception e) {
            logger.error("Failed to send email: ", e);
            return false;
        }
    }

    public static void main(String[] args) {
        String userName = "your-email@example.com";
        String password = "your-password";
        String smtpHost = "smtp.example.com";
        String to = "recipient@example.com";
        String cc = "cc-recipient1@example.com,cc-recipient2@example.com";
        String subject = "Test Email Subject";
        String body = "This is the body of the test email.";
        List attachments = Arrays.asList("path/to/file1.pdf", "path/to/file2.docx");
        MailService email = MailService.create(smtpHost, userName, password, to, cc, subject, body, attachments);
        email.send();
    }
}