Always Free DNS Tools
Since many DNS site starting to charge a fee for the DNS tools service. I recommend a free DNS Tools site will always be free.
The Domain Name System (DNS) associates various information with domain names; most importantly, it serves as the "phone book" for the Internet by translating human-readable computer hostnames, e.g. www.example.com, into IP addresses, e.g. 208.77.188.166, which networking equipment needs to deliver information. A DNS also stores other information such as the list of mail servers that accept email for a given domain. By providing a worldwide keyword-based redirection service, the Domain Name System is an essential component of contemporary Internet use. (Source: Wikipedia)
The list of tools offer for free are:
- DNS Lookup
- Reverse DNS
- Whois
- Test Email Servers
- Anti-Spam Blacklist
- Send Email as someone else
- Portscan
- Ping
- Trace Route
- Random Password
- Get a Web Server Type
- Open Relay Test
Most of the tools are using for Server Side Analyse and Tracking. It very useful for System Engineer and Web Master to monitor the server and web site.
One of the fantastic tools is the " Send email as some one else". This tools allow you to send email as some one else. You can check email blocking by address or domain. But your IP will included to prevent abuse.
Bookmarks this page now. Enjoys. 
