Currently RIPE – the European Body responsible for all things to do with IP addresses – are experiencing problems with their root DNS service.
This has resulted in a number of IP addresses losing their reverse DNS mappings. RIPE are working hard to resolve the problem, and will be posting more information on their status page as it becomes available.
At this time we do not believe any FidoNet customers are affected, however the full scale of the problem is still being addressed and a number of issues have culminated in problems, some of which have not become completely apparent as yet.