Ethereum Name Service - Like DNS, but for Ethereum wallet addresses
MxToolBox - All of your MX record, DNS, blacklist and SMTP diagnostics in one integrated tool.
How DNS Works - Super cute web comics about 'How DNS Works' for beginners!
Dnsstuff - DNSstuff offers DNS tools, Network tools, Email tools, DNS reporting and IP information gathering.
Elph Plasma - Highly scalable blockchain infrastructure for Ethereum
intoDNS - IntoDNS checks the health and configuration and provides DNS report and mail servers report.