MxToolBox - All of your MX record, DNS, blacklist and SMTP diagnostics in one integrated tool.
intoDNS - IntoDNS checks the health and configuration and provides DNS report and mail servers report.
Dnsstuff - DNSstuff offers DNS tools, Network tools, Email tools, DNS reporting and IP information gathering.
Nslookup - Little civil argument one of the completely essential administrations basic to the usefulness of the Internet is the Domain Name System (DNS).
DNSInspect - DNS is a free online service to check your domain’s servers for common DNS and mail errors and produces a report with explanations how to fix them.
DNS Checker Tool - Check Domain Name System (DNS) records for any website.