For our domains we’ve been utilizing quite popular free DNS service provided by xname.org. Apparently they struggled with database problems by the end of last year and started to refuse any dns lookup for our domains. It happens, but because of free nature of the service, there is no support at all. So emails routed to us got happily stuck all over the internet, our website was inaccessible as well as our whole infrastructure and I didn’t know what is going on. It took us one day to switch to paid DNS, but things should go smooth again. I’m sure that in the end it will be cheaper than xname.org anyway. 🙂