We’ve cleaned up the spam and restarted SMTP on server NC018 at 22:13 UTC. You can now send email again.
We continue to work against the spam, and are escalating the defences. We’ve seen a huge increase in spam the last couple of days from multiple sources, including from throwaway domains registered through a single, reputable registrar. Once we determine the IP addresses of that registrar’s mail servers, we’ll be blocking them until they stop hosting and doing business with spammers.
Once again we apologise for the inconvenience.