This blocklist is technically online but receives inconsistent maintenance. Its deliverability impact is lower than actively maintained lists.
What it is
Nether.net operated DNSBL zones for open relays and uncertain mail sources in the early-to-mid 2000s. The RELAYS zone targeted open SMTP relays that could be used to relay spam anonymously. These lists were active during a period when open relays were a major spam delivery mechanism.
How it affects SMTP delivery
Despite being deprecated, some legacy SpamAssassin configurations still include Nether zones in their DNSBL query sets. Depending on the zone's current DNS response behaviour, this may produce false positives or timeouts rather than meaningful filtering.
What causes a listing
Historical listings reflected open relay configurations or uncertain sending patterns.
How to get removed
No active removal process is available. If you are seeing Nether-related blocks, update your SpamAssassin configuration to remove the deprecated zones.
For the full reference catalog, see the email blocklist directory.
Delisting process in detail
The Nether blocklist (blacklist.woody.ch and related zones operated from Switzerland) targets spam sources observed by Swiss and European mail infrastructure. Delisting is handled through the operator’s contact form. Response times vary because Nether is operated by a small volunteer team, typically 24-72 hours for well-documented requests. Automatic decay occurs when the observed spam pattern stops, usually within 7-14 days. Nether is a smaller blocklist with regional focus rather than global coverage.
Prevention practices
Nether prevention follows standard anti-abuse fundamentals: authenticated sending, list hygiene, complaint monitoring. Because Nether operates in the European mail community, senders reaching European (particularly Swiss and German-speaking) recipients should monitor it specifically. Gradual IP warmup and consistent send patterns help avoid triggering Nether’s volume-based signals. Query the blocklist regularly for your sending IPs; Nether’s data is not always incorporated into commercial monitoring tools due to its smaller scale.
Common listing causes
Nether listings correlate with actual observed spam sending, typically from compromised shared-hosting accounts or from IPs used in coordinated spam campaigns. The volunteer operators focus on high-signal listings rather than broad enforcement, so Nether listings usually indicate real problems. Purchased lists that hit Swiss honeypots are the most common inadvertent cause for legitimate marketing senders; scraped lists containing harvested addresses trigger Nether traps within the first send.
Related blocklists
Nether operates alongside several other regional European blocklists: NIX Spam (German-speaking community), Backscatterer (Swiss operation), and various smaller lists maintained by regional ISPs. Enterprise senders reaching European recipients should monitor these regional lists alongside Spamhaus and other major blocklists. Nether’s smaller scale means it appears in fewer commercial monitoring products, which is why direct polling from your operations team is worthwhile.
About the Author
Alaa · LinkedIn
Email infrastructure specialist with 8+ years of hands-on experience in SMTP, deliverability, and email verification. I’ve configured and troubleshot mail systems across Postfix, Exchange, and cloud relays, managed IP reputation and warmup campaigns, and built verification pipelines processing millions of addresses. My work spans DNS authentication (SPF, DKIM, DMARC, BIMI), bounce handling, blocklist monitoring, and compliance frameworks including CAN-SPAM and GDPR. I write every article on SMTPedia to give email professionals, developers, and marketers the accurate, RFC-grounded reference they need.
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