群发消息返回数据结构：

{"ToUserName":"","FromUserName":"","CreateTime":"1712059446","MsgType":"event","Event":"MASSSENDJOBFINISH","MsgID":"3147487831","Status":"err(20431)","TotalCount":"0","FilterCount":"0","SentCount":"0","ErrorCount":"0","CopyrightCheckResult":{"Count":"0","ResultList":null,"CheckState":"0"},"ArticleUrlResult":{"Count":"0","ResultList":null}}

查看公众号文档，并未找到 20431 相关描述。