这对我有用：

msg = MIMEMultipart()
msg['From'], msg['To'], msg['Subject'] = ... # specify your sender, receiver, subject attributes
body = 'This is the body of the email.'
body = MIMEText(body) # convert the body to a MIME compatible string
msg.attach(body) # attach it to your main message

您附加了正文到 msg ，而 body 应该是 MIMEText 对象。

You attach the body to the msg, and body in your case should be the MIMEText object.