The ORB UK Open Relay Block Zone (ORBZ) Manual is a manually generated blocklist (or blacklist) containing IP addresses that have been identified as open SMTP relays, which can be used to distribute unsolicited email.
The ORB UK Open Relay Block Zone (ORBZ) Manual is a manually generated blacklist that lists IP addresses of servers believed to be open SMTP relays. An open relay is a mail server that is configured to accept and forward email from any user, anywhere, which makes it a prime target for spammers to exploit.
The policy of this blocklist is to publicize the existence of these open servers to highlight a potential cause for the high volume of unsolicited commercial email (UCE). ORB UK does not directly block any email. Instead, they operate as a trusted third party. System administrators who use this blacklist query the ORB UK database to check if an incoming email's source IP is listed. Based on the simple "yes" or "no" response, the administrator's own system decides whether to accept or reject the email. This makes it a DNS-based blocklist (DNSBL).
Many system operators trust this blacklist because open relay lists have historically been an effective tool against spam. They believe any open server can be used for malicious purposes and choose not to accept mail from them.
ORB UK is the organization that publishes the Open Relay Block Zone (ORBZ) manual blacklist. ORBZ refers to the list itself, which was originally created by Alan Brown. ORB UK maintains and publishes this list, asserting their right to do so as fair comment in the public interest. They state that the purpose is to publicize servers that are, or are likely to be, used for sending spam. The organization also acknowledges contributions from other individuals in developing and maintaining the backend software for the service.
If you are the postmaster or system administrator for a server on this blocklist, you can request removal. However, before you do, you must ensure your server is no longer an open relay. Threatening the organization will not lead to delisting.
Be aware that if your server is found to be an open relay again in the future, it will be immediately relisted on the blacklist.
The impact of being listed on the ORB UK Open Relay Block Zone (ORBZ) Manual is considered low. This suggests that this specific blocklist is not as widely used by major email providers and corporations as other more prominent blacklists. However, a low impact rating does not mean there is no impact. Any mail server administrator who chooses to use this blacklist will reject mail from your IP address, which can lead to deliverability problems with those specific recipients. It is always best practice to secure your server and request removal from any blacklist (or blocklist) you appear on.
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