使用smtplib发送电子邮件，没有错误但没有消息传递

import smtplib
from email.mime.text import MIMEText

def send_email():
    # 邮件服务器配置
    smtp_host = 'smtp.example.com'
    smtp_port = 25
    smtp_user = 'your_username'
    smtp_password = 'your_password'

    # 邮件内容
    sender = 'sender@example.com'
    receiver = 'receiver@example.com'
    subject = 'Test Email'
    body = 'This is a test email.'

    # 创建邮件对象
    msg = MIMEText(body, 'plain')
    msg['Subject'] = subject
    msg['From'] = sender
    msg['To'] = receiver

    try:
        # 连接邮件服务器并发送邮件
        server = smtplib.SMTP(smtp_host, smtp_port)
        server.login(smtp_user, smtp_password)
        server.sendmail(sender, receiver, msg.as_string())
        server.quit()
        print('Email sent successfully!')
    except Exception as e:
        print('Failed to send email:', str(e))

send_email()