That's exactly what they did. "The distribution list has been removed and associated emails are being traced and cleared." See http://support.nhs.net/servicestatus
That's exactly what they did do though. See http://support.nhs.net/servicestatus by 09:45 they'd disabled the distribution list and updated their service status page. There were that many emails in the system that at 15:30 people were still receiving emails sent at 09:30.