DNS | Web Developer Blog

Check Old IP of a Domain Name

http://viewdns.info/iphistory/

Creating an SPF Record for Your Zoho Domain Name

Add this TXT record:
v=spf1 mx include:zoho.com ~all

Reference:
http://www.zoho.com/mail/help/faq/#oc106

Creating an SPF Record for Your Google Apps Domain Name

Add this TXT record:
v=spf1 a include:_spf.google.com ~all

Reference:
http://support.google.com/a/bin/answer.py?hl=zh-Hant&topic=2759192&ctx=topic&answer=178723

Test if a domain is blocked in China

Test if any website is Blocked in China in real-time

Check DNS Zone

http://pingability.com/zoneinfo.jsp

http://www.dns-info.cz/

https://www.ultratools.com