我试图在服务器上设置SPF – 邮件工作正常并根据mxtoolbox和其他在线检查验证但是当我使用
http://www.kitterman.com/spf/validate.html检查它时出现错误：
PermError SPF Permanent Error: Void lookup limit of 2 exceeded
我知道有10个查找的限制,但之前没有看到过这个错误.
SPF记录是：
v=spf1 a mx ip4:IP1 ip4:IP2 ip6:IP3 include:spf-a.outlook.com include:spf-b.outlook.com include:spf-c.outlook.com include:spf.messaging.microsoft.com include:_spf.zdsys.com include:spf.mail.intercom.io -all
什么是空的查找限制参考？
解决方法
void查找限制为
introduced in RFC 7208,指的是DNS查找,它返回空响应(NOERROR没有答案)或NXDOMAIN响应.这是10个DNS查找总计数的单独计数.
As described at the end of 07001,there may be cases where it is useful to limit the number of “terms” for which DNS queries return either a positive answer (RCODE 0) with an answer count of 0,or a “Name Error” (RCODE 3) answer. These are sometimes collectively referred to as “void lookups”. SPF implementations SHOULD limit “void lookups” to two. An implementation MAY choose to make such a limit configurable. In this case,a default of two is RECOMMENDED. Exceeding the limit produces a “permerror” result.
这有助于防止错误或恶意的SPF记录导致基于DNS的拒绝服务攻击.
在您的情况下,问题部分似乎是：
include:spf.messaging.microsoft.com
其SPF记录是：
v=spf1 ptr:protection.outlook.com ptr:messaging.microsoft.com ptr:o365filtering.com -all
如果查找这三个记录,则返回没有记录的NOERROR或NXDOMAIN.
由于三条记录没有返回任何内容,因此超出了void查找限制2,并且SPF记录失败.