What it is
The Passive Spam Block List (PSBL) is a lightweight DNSBL maintained by Len Conrad and operated on surriel.com infrastructure. It lists IP addresses that send mail to PSBL's spam trap addresses. The list is designed to be simple and low-noise, with a focus on minimising false positives and requiring no human intervention for listings or removals.
How it affects SMTP delivery
PSBL is used by a smaller subset of mail servers compared to Spamhaus or SpamCop, but it is included in some composite DNSBL query services. A PSBL listing typically contributes to spam scoring rather than outright blocking, though some MTAs do configure it as a hard reject.
What causes a listing
Listings occur exclusively when your IP sends mail to PSBL trap addresses. This is most commonly caused by sending to purchased lists, scraped addresses, or very old lists that include trap addresses.
How to get removed
PSBL listings expire automatically within 24-48 hours after your IP stops sending to trap addresses. There is no manual removal process. Check listing status at psbl.surriel.com.
For the full reference catalog, see the email blocklist directory.
Delisting process in detail
The Passive Spam Block List (PSBL) is unusual among DNSBLs: it operates strictly on trap-hit data (spam messages received by PSBL’s honeypot network) and offers immediate self-service delisting through psbl.org’s lookup form. There is no waiting period, no fee, no manual review: enter the listed IP, confirm the delisting, and PSBL removes the entry immediately. However, PSBL will re-list the IP if new trap hits occur, so delisting without underlying remediation is only a temporary fix. The self-service delisting policy is designed for legitimate senders who need to unblock quickly while investigating the root cause.
Prevention practices
PSBL prevention requires eliminating trap hits, which means removing invalid addresses from your sending lists before they hit honeypots. Use double opt-in for all list additions, promptly suppress hard bounces (a common source of trap hits when old lists contain recycled addresses), and honor unsubscribes quickly. Never purchase or scrape lists: PSBL honeypots are seeded through address harvesting from public web pages, so scraped lists have a high probability of hitting traps. Regular list hygiene through validation services (before sending, not during) reduces trap exposure significantly.
Common listing causes
PSBL listings almost always result from trap hits, typically from three patterns: purchased or rented lists containing harvested honeypot addresses, old lists where recycled addresses have been converted into honeypots by ISPs, and compromised sending accounts blasting to whatever address database the attacker uploaded. The trap hit rate correlates with list quality: a clean double-opt-in list typically produces zero trap hits over years, while a purchased list can hit multiple traps within the first send.
Related blocklists
PSBL sits alongside SpamCop and CBL as one of the fast-reacting trap-hit blocklists. Its self-service delisting distinguishes it from stricter lists like Spamhaus SBL, where remediation must be documented before removal. PSBL is queried by many mid-market mail servers and appliances but has less impact at major mailbox providers (Gmail, Outlook, Yahoo) that rely primarily on internal reputation. Monitoring PSBL alongside Spamhaus ZEN, SORBS, and Barracuda gives comprehensive coverage of the main IP-based reputation signals.
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.
About SMTPedia
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