Frequently Asked Questions

What is Reverse DNS Lookup? 甚麼是反向DNS解釋?
Last Updated 2 months ago

Reverse DNS lookup (rDNS) is a process to determine the hostname or host associated with a given IP address.

By using Reverse DNS Lookup, you may be able to identify the domain name of a spammer sending you spam email or the domain name of a computer trying to break into your firewall or someone trying to hack your system. You may also be able to use this information to determine the name of the internet service provider assigned to a particular IP address

One e-mail anti-spam technique is to check the domain names in the rDNS to see if they are likely from dialup users, dynamically assigned addresses, or home-based broadband customers. Since the vast majority, but by no means all, of e-mail that originates from these computers is spam, many mail servers also refuse e-mail with missing rDNS names.

There are many large ISPs and companies who require Reverse DNS, below are some examples:


反向DNS解釋 (rDNS) 是利用DNS解釋一個特定的IP地址的主機名稱。

透過反向DNS解釋, 你可以找出向您發送垃圾郵件的域名, 或者是試圖入打破你的防火牆的主機名稱, 或試圖入侵你的系統的主機名稱。你也可以利用這個信息來確定一個特定的IP地址是由那一個互聯網服務供應商所分配到.

其中一個反垃圾郵件技術是檢查域名的 rdns ,以了解他們是否有可能從撥號上網用戶,動態分配的地址,或是寬頻用戶。由於絕大多數從這些電腦發出的電子郵件都是垃圾郵件,所以許多郵件伺服器會拒絕接收來自沒有設定反向DNS解釋的伺服器.

有很多其他的大型互聯網供應商以及其他公司, 都會要求反向DNS的, 以下是一些例子:

AOL
http://www.aol.com , http://www.aol.hk

Comcast
http://www.comcast.net

Corkscrew International
http://v004.corkscrew.vg

Spamhaus
http://www.spamhaus.org

Spamcop
http://www.spamcop.net

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