I use Zoneedit for DNS "hosting". They give great, free service, with additional features at small costs.
For updating my Dynamic IP, I use the DDClient script (supports zoneedit, dyndns.org and many other providers)
A few days ago (according to my logs: 30/05/08 18:15:00 UTC) DDClient stopped updating my IP in Zoneedit. Apparently Zoneedit changed the URL, and ddclient.conf should be updated accordingly:
It probably hurt many users.. I hope I didn't lose too many emails =)
Update: I notified ddclient developers and it was fixed (in SVN only currently).
Update 2: According to wimpunk (ddclient developer), the "server=www.zoneedit.com" can be simply commented-out from ddclient.conf (it's an optional parameter!); when commented-out, default already uses the correct address (dynamic.zoneedit.com), even in 3.7.3 or earlier.