intoDNS - IntoDNS checks the health and configuration and provides DNS report and mail servers report.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
MxToolBox - All of your MX record, DNS, blacklist and SMTP diagnostics in one integrated tool.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
SolveDNS - SolveDNS works to check your name servers, a records, and mail servers, SOA records for errors, consistency, efficiency and speed using several DNS tests.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.