In the past, I used checkdns.net for testing of a domain was configured correctly (including DNS and MX settings).
However, checkdns.net seems to be down or dead.
Luckily, intoVPS (with VPS servers in Amsterdam (Netherlands), Atlanta (USA), Cluj-Napoca (Romania) and Fremont (USA)) started lauched intoDNS a few years ago, and it works at least as good as checkdns.net used to work.
–jeroen
