类型 错误编号 原因 rbl message 554 外部黑名单external blacklist. rate control messages 554 连接数过多too many connections. 消息过多too many messages. 速率控制rate control. timeout message 421 中断abort. 发件人超时sender timeout no such domain message 550 不存在的域no such domain. 非法域invalid domain. no such user message 550 不存在收件人no such user. 非法收件人invalid recipient. blocked subject message 550 主题非法illegal subject containing “(.*)”. subject. [Read More →]