<dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

spring:
  mail:
    host: smtp.163.com
    username: *****@163.com
    password: *****
    port: 25

public interface SendMailService {
    public String sendSimpleMail(String address, String subject, String body);
    public String sendAttachmentMail(String address, String subject, String body, MultipartFile attach) throws MessagingException, IOException;
}

@Service
public class SendMailServiceImpl implements SendMailService {
    @Autowired
    private JavaMailSender javaMailSender;
    @Value("${spring.mail.username}")
    private String account;

    /**
     * @param address 收件地址
     * @param subject 標題
     * @param body    正文
     * @return
     */
    @Override
    public String sendSimpleMail(String address, String subject, String body) {
        SimpleMailMessage smm = new SimpleMailMessage();
        smm.setFrom(account);
        smm.setTo(address);
        smm.setSubject(subject);
        smm.setText(body);
        javaMailSender.send(smm);
        return "發(fā)送成功";
    }

    /**
     * @param address 收件地址
     * @param subject 標題
     * @param body    正文
     * @param attach  附件
     */
    @Override
    public String sendAttachmentMail(String address, String subject, String body, MultipartFile attach) throws MessagingException, IOException {
        MimeMessage mimeMailMessage = javaMailSender.createMimeMessage();
        MimeMessageHelper mimeMessageHelper = new MimeMessageHelper(mimeMailMessage, true);
        mimeMessageHelper.setFrom(account);
        mimeMessageHelper.setTo(new String[]{address});
        mimeMessageHelper.setSubject(subject);
        mimeMessageHelper.setText(body);
        // 獲取附件的文件名和后綴名
        String fileName = attach.getOriginalFilename();
        String fileExtension = fileName.substring(fileName.lastIndexOf(".") + 1);
        // 讀取附件內(nèi)容
        byte[] bytes = attach.getBytes();
        // 創(chuàng)建一個新的資源對象來存儲附件內(nèi)容
        ByteArrayResource attachmentResource = new ByteArrayResource(bytes);
        // 添加附件，使用完整的文件名（包括后綴名）
        mimeMessageHelper.addAttachment(fileName, attachmentResource);
        javaMailSender.send(mimeMailMessage);
        return "發(fā)送成功";
    }
}

@RestController
public class EmailController {
    @Autowired
    private SendMailService sendMailService;
    @RequestMapping("/sendMail")
    public String sendMail(String address, String subject, String body) {
       return sendMailService.sendSimpleMail(address, subject, body);

    }
    @RequestMapping("/sendMailWithAttachment")
    public String sendMailWithAttachment(String address, String subject, String body, MultipartFile attach) throws IOException, MessagingException {
       return sendMailService.sendAttachmentMail(address, subject, body, attach);
    }
}