I wasn’t going mad yesterday. My OneAndOne (1&1) hosted domains really did disappear from the web.
Seems they had some sort of DNS ‘overload’ problem – response to my support call yesterday:
“Thank you for contacting us.
We sincerely apologize for the inconvenience that this had caused you. DNS propagation for domains has been interrupted due to overload on the system which resulted to an intermittent on the connection for the Website and emails of the domains. Our system specialists have resolved the concern and have monitored this case to avoid future downtime of service. Thank you so much for your patience while we have worked on the resolution.
If you have any further questions please do not hesitate to contact us.”

