Summary: We've added further RBLs to our mailservers. We do operate an SMTP AUTH by-pass mechanism so if you're having trouble sending e-mail please turn SMTP authentication in your e-mail client.
The follow KB article will give you instructions on how to do this for most clients:
https://support.blacknight.ie/472/smtp-authentication.html
We aware of an issue with Sorbs at the moment where a lot of our IP Addresses, including those of our Qmail cluster, are being listed incorrectly as dynamic. We are in contact with Sorbs and trying to get it sorted, however they seem to having serious issues with their site at the moment which may be related. Note: our Hosted Exchange service is not effected.
There is nothing we can do to correct this at the moment, we have to wait for Sorbs to get the issue sorted.
UPDATE 15:45: It seems that Sorbs have now emptied the blacklist that was causing the issue. The TTL (Time-To-Live) for those records is one hour, so hopefully within the next hour we see the last of the block.
We have been contacted by several clients who are having issues sending and receiving emails to various ISPs and companies.
We at Blacknight ARE NOT using ORDB as it is defunct, however it is obvious that quite a few people still are. We cannot assist you, as the mail servers affected are not under our control.
If you have issues sending mails please check the error message. If there is a reference to ORDB you will need to contact the person / company you are sending the mail to.
Some of you might remember relays.ordb.org going offline a couple of years ago. It was one of the widely used, free, DNS Blacklists.
Yesterday at some point they started them backup and they appear to have blacklisted every single IP address.
Our monitoring system checks all configured IPs on all nodes against blacklists of this kind and sends you a notification via email or sms if one of your IPs gets on a list.
Please ignore these, but check all your mail servers to make sure they are not blocking based on "relays.ordb.org".