如何在python中通过smtplib向多个用户发送电子邮件？

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

def send_email(subject, message, recipients):
    # 邮件内容
    msg = MIMEText(message, 'plain', 'utf-8')
    msg['Subject'] = Header(subject, 'utf-8')
    msg['From'] = 'sender@example.com'
    msg['To'] = ', '.join(recipients)

    # SMTP服务器配置
    smtp_server = 'smtp.example.com'
    smtp_port = 587
    smtp_username = 'your_username'
    smtp_password = 'your_password'

    # 连接SMTP服务器并发送邮件
    try:
        server = smtplib.SMTP(smtp_server, smtp_port)
        server.starttls()
        server.login(smtp_username, smtp_password)
        server.sendmail('sender@example.com', recipients, msg.as_string())
        server.quit()
        print('邮件发送成功')
    except Exception as e:
        print('邮件发送失败:', str(e))

# 调用函数发送邮件
subject = '测试邮件'
message = '这是一封测试邮件。'
recipients = ['user1@example.com', 'user2@example.com', 'user3@example.com']
send_email(subject, message, recipients)