SORBS is Closing IP Blacklisting Operations After 20 Years

06 June 2024

SORBS (Spam and Open Relay Blocking System), a widely-used IPv4 blacklist of email servers known for blocking spam, has shut down.

SORBS operated as a donation-based nonprofit that distributed its blocklist as free and open-source, was no longer financially viable, according to industry experts. Additionally, while SORBS was widely used in its early days, enterprise spam filtering had largely transitioned to more advanced spam filtering solutions.

The service was shut down on June 5, 2024, and its website has been replaced with the message

“Site down permanently. Please note that this service has been decommissioned and will no longer contain reputation data. Given the wide range of potential replacement solutions in the market, Proofpoint cannot make specific recommendations nor endorse any specific replacement product.”

SORBS launched in 2001, and launched a DNS-based, publicly-distributed distributed blocklist, eventually reaching over 12 million addresses, according to an archived history page on the SORBS site. In 2011, it was acquired by Sunnyvale-based Proofpoint.

SORBs IPv4 Blacklist Service Closing Down

SORBS was one of the Original DNSBL Services

While it was one of the oldest DNSBL services, the sunsetting of SORBS is unlikely to cause a a major disruption in email delivery. Widely used in the early 2000s, in later years primarily assisted hobbyist email administrators in filtering spam and malicious email traffic.

But it marks a shift in the tech industry, from free and open-source software projects to proprietary enterprise software. While it was still a viable product, the model of the free and open internet has shifted significantly toward an enterprise model, which allows for greater investment in development, but a major shift in the culture of IT, and in this case, at the cost of a viable product.

Its influence and reach had declined in recent recent years, as evidenced in this Reddit thread from 2021, where an email marketer was listed on SORBS, and many of the responses advise ignoring it, as the major tech firms were not using it.

After SORBS, Other Options for Spam Filtering

There are still available distributed blocklists for spam similar to SORBS. some alternatives there are:

  • Spamhaus
  • Barracuda Central
  • Spamcop

While Proofpoint is sunsetting SORBS, it still maintains spam filtering services as an enterprise product. After acquiring SORBS in 2011, Proofpoint chose not to monetize it, and did not intervene in its operations, and launched Proofpoint-branded enterprise spam filtering services.

Although SORBS was a pioneer, and did serve a significant role in the IT community in years past, its presence has waned as newer services have emerged, and by 2024 was a niche product. So its shutdown is unlikely to have a major impact on enterprise security and email operations.

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