DNSsy, love it.
One of the tools that I use to admin servers used to be DNSreport from DNSstuff.com. It was an invaluable tool to diagnose problems related to DNS and emailing. Most of the basic issues are sometimes overlooked whilst configuring servers and it can drive you up the wall if you don’t cover the basics again (properly).
Since DNSstuff requires you to pay (atleast the last time I checked), once my subscription expired I looked else where.
DNSsy is one of those tools that I now use. It does a similar job to DNSreport but it is free and easy to use. We recently fixed a bug with emailing with the help of DNSsy.
