A little while ago, I was playing with DNS entries. I was having a few issues here and there with DNS and mail configuration. After doing some research, I came across DNS Report which was absolutely brilliant for troubleshooting my problems. DNS Report is related to DNS Stuff which has many more tools to test domains, IP's, hostnames and more.
On a side note, I have been using DNSExit for my DNS services including backup MX. Their DNS services are great, but the backup MX at $20USD/domain was a bit steep. I have now just found EditDNS which has better services that are either cheaper or free. EditDNS also has a blog which makes it easy to keep in touch with their developments.
Tags: Great Tools, Useful Links