domain-name-system – 为什么我的isp建议不要使用IP作为MX？

我想知道为什么我曾多次听说直接输入IP作为MX记录是不好的.大多数ISP建议我们使用邮件服务器IP创建A记录,并将该A记录用作MX记录.

我之前输入了一个IP作为MX,它大部分时间都在工作,但有些情况下它不起作用.似乎无法找到原因.

对此有合理的解释吗？

解决方法

与DNS和邮件交换相关的各种RFC指定MX记录由首选项值和具有地址(A)记录的域名组成.

见RFC 2181,section 10.3:

10.3. MX and NS records

The domain name used as the value of a NS resource record,or part of
the value of a MX resource record must not be an alias.  Not only is
the specification clear on this point,but using an alias in either
of these positions neither works as well as might be hoped,nor well
fulfills the ambition that may have led to this approach.  This
domain name must have as its value one or more address records.
Currently those will be A records,however in the future other record
types giving addressing information may be acceptable.  It can also
have other RRs,but never a CNAME RR.