Python发送没有内容的电子邮件

import smtplib
from email.mime.text import MIMEText
from email.header import Header

def send_email(sender, receiver, subject):
    # 创建一个空的邮件对象
    message = MIMEText('', 'plain', 'utf-8')
    message['From'] = Header(sender, 'utf-8')
    message['To'] = Header(receiver, 'utf-8')
    message['Subject'] = Header(subject, 'utf-8')

    try:
        # 连接SMTP服务器
        smtp_obj = smtplib.SMTP('smtp.example.com', 25)
        # 登录SMTP服务器
        smtp_obj.login('username', 'password')
        # 发送邮件
        smtp_obj.sendmail(sender, receiver, message.as_string())
        print("邮件发送成功")
    except smtplib.SMTPException as e:
        print("邮件发送失败：" + str(e))
    finally:
        # 关闭连接
        smtp_obj.quit()

# 调用函数发送邮件
send_email('sender@example.com', 'receiver@example.com', '测试邮件')