163经销代理服务商：深圳市阔步实业有限公司

550 5.7.1 Client host rejected: Your message was rejected due to spam filtering

553 5.7.1 [BL21] Connections will not be accepted from 121.50.xx.xx because the ip is in Spamhaus's list

553 delivery from 121.50.xx.xx is rejected. The connecting IP is blocked  using zen.spamhaus.org

550 #5.7.1 Your access to submit messages to this e-mail system has been rejected. 

退信原因：发信服务器的IP在RBL黑名单

解决方案：IP被spamhaus列入了黑名单，可以直接去官网解封即可，只要你不是发垃圾邮件的机器，一般都是可以解封的，如果是发垃圾邮件的，整个段被SBL的，一般只有IP所有者跟他们联系，才能解封，网易邮箱220.181.0.0/20被全部黑名单，就是这样，只有北京电信跟他们联系，才能解封，私人是没法解封的