Just received this update from my Exchange service provider about email problems with Network Solutions.
Service Advisory: [my provider] has discovered a possible issue with certain Network Solutions name servers. When looking up DNS information for domains hosted on Network Solutions or when querying Network Solutions name servers, we have seen intermittent time outs. This issue was discovered when customer reported bounce backs for people trying to send them mail. People sending to domains hosted on these servers may receive similar bounce backs. After some research, we found reports of similar issues by other companies (outside of [my provider]) and reports from Network Solutions stating that there may be a Denial of Service Attack (DDOS). We will monitor this issue and provide an update when the issue has been resolved by Network Solutions.
Such a shame that a company the size of Network Solutions allows this to happen. Top shelf Dynamic DNS provider Dyn, aka Dynamic Network Services, Inc and DNS provider OpenDNS figured out DNS long ago.