通过python发送HTML电子邮件，格式错误

Question

我构建了一个abodexd设计，将其转换为html代码，然后将整个代码放入文本文件中，这样我就可以使用while open()函数通过电子邮件发送它。但问题是整个格式都不对。你知道吗

This is a correct format

This is a format in email which I get

  EMAIL = f'{login_email}'
    PASSWORD = f'{login_email_pass}'

    message = EmailMessage()
    message['Subject'] = f'{program_name} : {SessionID} Server Launch verification'
    message['From'] = EMAIL
    message['To'] = test_email
    message.set_content('This email is sent using python.')
    #with open('messages.txt', mode = 'r' , encoding= 'UTF-8') as oap:
        #z = oap.read()

    message.add_alternative(f"{z}", subtype = 'html')