The ORB UK Open Relay Block Zone (ORBZ) Inputs is a public blacklist (or blocklist) that identifies IP addresses believed to be open SMTP relays, which are systems often exploited to send unsolicited bulk email.
The ORB UK Open Relay Block Zone (ORBZ) Inputs is an automatically generated blacklist that identifies open SMTP relays. The core policy is to list servers that are tested and confirmed to be open relays, which are often exploited to send unsolicited bulk email (spam). ORB UK does not block any email directly. Instead, it acts as a trusted third-party data source. System administrators at various organizations use this blocklist to inform their own mail server policies.
When an email arrives at a server using this blacklist, the receiving server queries ORB UK to check if the sending IP address is on the list. ORB UK provides a simple 'yes' or 'no' answer based on its test results. The local system administrator then decides whether to accept, reject, or quarantine the email based on that information. The primary goal of this blocklist is to publicize the existence of open mail servers, highlighting a potential security vulnerability that can contribute to the spread of spam.
The list is published by an organization known as ORB UK. They describe the list as a form of 'Fair Comment in the public interest'. The list was originally created by Alan Brown and is now maintained and published by ORB UK. They state their right to publish the blacklist is protected under various freedom of speech laws, including Article 10 of the European Convention on Human Rights and the First Amendment to the Constitution of the United States.
Several individuals, including Craig Sanders, Donnell Kirwan, and Gareth Harmer, have been acknowledged for their contributions to the software and scripts that operate the service.
To request removal from this blacklist, the postmaster or system administrator of the listed server must first ensure the open relay has been closed. Once you have secured your server, you can begin the delisting process.
ORB UK explicitly states that the fastest way to get delisted is to close the open relay on your server. Sending threats will not result in removal.
The impact of being on the ORB UK Open Relay Block Zone (ORBZ) Inputs blacklist is considered low. This suggests that the list is not used by a large number of major mailbox providers or corporations. However, a listing can still cause email delivery problems if your recipients' mail servers do use this specific blocklist. Any delivery issues will be confined to receivers that subscribe to this particular data feed, but it's always best practice to resolve the underlying issue (the open relay) and request delisting to ensure maximum deliverability.
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