错误含义：

•554 DT:SPM 发送的邮件内容包含了未被许可的信息，或被系统识别为垃圾邮件。请检查是否有用户发送病毒或者垃圾邮件；
http://help.163.com/09/1224/17/5RAJ4LMH00753VB8.html

说明：代码里没有指定发收件人

修改之前：

message = MIMEMultipart()
message.attach(textApart)
message.attach(xlsxApart)
message['Subject'] = 'new notification'

修改之后：

message = MIMEMultipart()
message.attach(textApart)
message.attach(xlsxApart)
message['From'] = sender
message['To'] = receivers[0]
message['Subject'] = 'new notification'

完整示例：

def sendMail(msg):
    """
    发送邮件
    msg: 正文内容
    """
    mail_host = 'smtp.163.com'
    mail_user = 'xxx'
    mail_pass = 'xxxx'
    sender = 'DJ-163<xxx@163.com>'
    receivers = ['DJ-QQ<xxx@qq.com>']

	# 文本
    textApart = MIMEText(msg, 'plain', 'utf-8')

	# 附件
    xlsxFile = fileName
    xlsxApart = MIMEApplication(open(xlsxFile, 'rb').read())
    xlsxApart.add_header('Content-Disposition',
                         'attachment', filename=xlsxFile)

	# 构建邮件
    message = MIMEMultipart()
    message.attach(textApart)
    message.attach(xlsxApart)
    message['From'] = sender
    message['To'] = receivers[0]
    message['Subject'] = 'new mail'

    try:
        smtpObj = smtplib.SMTP()
        smtpObj.connect(mail_host, 25)
        smtpObj.login(mail_user, mail_pass)
        smtpObj.sendmail(
            sender, receivers, message.as_string())
        smtpObj.quit()
        print('邮件已经成功发送！')
    except smtplib.SMTPException as e:
        print('邮件发送失败', e)  # 打印错误