550 Service unavailable; Client Host [xx.xx.xx.xx] blocked using Trend Micro RBL+-MDaemon最好用的邮件系统-企业邮箱-邮件服务器

退信内容： 550 Service unavailable; Client Host [xx.xx.xx.xx] blocked using Trend Micro RBL+. Please see http://www.mail-abuse.com/cgi-bin/lookup?ip_address=xx.xx.xx.xx

退信原因：被趋势科技列入黑名单，需要申诉处理

解决办法：根据退信内容打开地址：http://www.mail-abuse.com/cgi-bin/lookup?ip_address=xx.xx.xx.xx，我们可以看到该IP地址被列入DUL列表中：

趋势科技查询结果

在趋势科技列表说明中我们可以发现可能被列入的原因：

为什么会进DUL黑名单

趋势科技提供了四个步骤来移除黑名单：

Step 1：Determine Your IP Address

Step 2：Check the Status of Your IP Address

Step 3：Send a Removal Request

Step 4：Investigation

点击下方的 “Request to be removed from the global blocked list” 来申请移除黑名单。

申诉界面

申述后的回复邮件：

The IP is listed on the DUL because it is not defined in rDNS as

static. Please follow the steps from previous email. If you are not the

mail administrator, you will need to work with your ISP to correctly

define the IP, then ask them to contact us at

dul@mail-abuse.com

Then we can work with the ISP to resolve the issue and remove your IP.

根据邮件内容，用户需要给自己邮件服务器出口的公网IP做反向解析，做好后用户可以用nslookup命令来检测是否生效，然后再申请移除黑名单。