Goolge GSuite Tools checks your name servers, A records, mail servers, SOA records for errors, consistency, accuracy and speed using several DNS tests. You can also flush your domain from Google's Recursive DNS Servers.
SolveDNS.com - SolveDNS is a great tool for troubleshooting DNS problems
SolveDNS checks your name servers, A records, mail servers, SOA records for errors, consistency, accuracy and speed using several DNS tests. SolveDNS does not cache any test results, so you get a fresh report everytime you run the test for your domain names. If you would like to see more tests or have a question or a comment about a test result, please don't hesitate to use the email address in the footer.
intoDNS.com - intoDNS is a great tool for DNS Health Checking
IntoDNS checks the health and configuration and provides DNS report and mail servers report.
And provides suggestions to fix and improve them, with references to protocols’ official documentation.
Tools to check your DSN SPF records or Sender Policy Framework. SPF Testing
DNSChecker.org - A DNS propagation check of various points around the world.
DNS Checker provides free dns lookup service for checking domain name server records against a randomly selected list of DNS servers in different corners of the world. Do a quick look up for any domain name and check DNS data collected from all location for confirming that website is completely propagated or not worldwide.