Tools For DNS Testing and Validation

Here are some of the websites that I often use for DNS validation or testing from external network perimeter.
Whenever you do email troubleshooting, website lookup, and or domain whois, you will find that these websites are quite helpful.

1. www.dnsstuff.com > This is the best one I think. It has a lot of tools and the result are very accurate and fast. You can query and get almost every information here. However you have to pay to get the service. They are not free anymore. Trial period are available.
2. www.zonedit.com/smtp.html > You can send email testing from this website for validation or troubleshooting. All you have to do is put the email server MX record, sender address, and recipient address.
3. www.mxtoolbox.com > Through this tool you can query MX record from a domain name.
4. http://network-tools.com/nslook > You can do NSLookup query for A record, CNAME, PTR, MX, NS, etc to certain server through this tool.
5. http://www.dnstools.com/ > Besides getting IP whois information, you can also do port checking status from this website.