We have taken the unusual step of blocking mail to and from certain domains on our primary mail server that are not (to our knowledge) sources of spam. These domains are:
We have blocked email to these domains because their mail servers — all hosted by the same company — while appearing to be up, do not accept any email. Instead of immediately rejecting email with either permanent (5xx) or temporary (4xx) errors, they hold open the connection from our mail server until it times out. This has a significant negative impact on other email sent by our clients.
Adding to the issue is that the domains associated with the mail servers and nameservers of their hosting provider — smtpdaemon.net and dnsdaemon.net — do not resolve to websites, and the identity of the owner of these domains is hidden behind a WHOIS privacy service. This means that this hosting company does not want to reveal who they are or how to contact them.
We regret the necessity to make this decision, and will revisit it in the future should circumstances change or if new or changed information is brought to light.
As always, please contact NinerNet support should you have any questions or concerns.