Are you on a blacklist?
Check any IP address or sending domain against 84 DNS-based blocklists including Spamhaus SBL/CSS/XBL, Barracuda, SORBS, UCEPROTECT, SURBL, Invaluement and the major mailbox-provider feedback loops.
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What we check, and why it matters.
- Spamhaus SBL · CSS · XBL · DBL · ZEN: the most consequential blocklist in email. A single SBL listing drops Gmail/Outlook placement to near zero within hours.
- Barracuda Reputation Block List: used by Barracuda email security appliances in tens of thousands of enterprises.
- SORBS · DUHL · SPAM: historical depth, used by some receivers as a secondary filter.
- UCEPROTECT level 1, 2, 3: aggressive but still consulted by some smaller receivers.
- SURBL · Invaluement IVMSIP24 · PSBL: domain-name and IP-network blocklists.
- +78 other DNSBL zones: full list available on request.
- Identify the listing reason. Each blocklist publishes the cause: spam-trap hit, snowshoe pattern, content trigger, complaint volume. Do not guess; read the listing record.
- Fix the root cause. Delisting without fixing the underlying issue results in re-listing within 48 hours. Common causes: list hygiene, content patterns, authentication gaps.
- Submit the delist request with evidence. Spamhaus accepts well-documented requests within 7-14 days. Other blocklists vary; some are automatic on inactivity, some require manual review.
- Don't send while listed. Continued sends to a listed IP accumulate complaints and reinforce the listing decision.
- Consider migration to clean infrastructure. If the listing is on infrastructure you don't control, sometimes moving is faster than fighting.
We provide hands-on Spamhaus delisting and reputation recovery as part of our managed warmup. If you're listed and need a path forward, the conversation starts on Telegram.
Not all listings are equal. Knowing which to act on first.
The check returns a status per RBL: clean, listed, or unreachable. Listed status further indicates which blocklist (Spamhaus SBL, CSS, XBL, DBL, PBL; Barracuda; SORBS variants; UCEPROTECT level 1/2/3; SURBL; Invaluement; Lashback UBL; Mailspike; the long tail of smaller DNSBLs). What you do about a listing depends entirely on which blocklist; treating them as equal wastes effort on listings that don't matter and underweights listings that do.
Tier 1: Spamhaus, Barracuda, Microsoft.
These are the listings that materially affect inbox placement at major receivers. Spamhaus SBL listing appears in Gmail's, Outlook's, Yahoo's, and most other major receivers' threat intel; SBL-listed mail typically arrives in spam folder if it arrives at all. Barracuda BRBL is consulted by a substantial portion of corporate mail filters globally. Microsoft's internal SNDS isn't a public RBL but corresponds to similar reputation decisions at Outlook and Hotmail. If the audit flags a tier-1 listing, treat it as urgent.
Tier 2: SORBS, UCEPROTECT levels 1-2, SURBL.
These are consulted by some receivers, particularly smaller European providers, corporate filters using MailScanner or similar stack, and academic mail systems. A listing here doesn't catastrophically break inbox placement everywhere, but it does affect a meaningful share of recipients. Worth addressing within days, though not the same day urgency as tier 1.
Tier 3: UCEPROTECT level 3, lesser-known DNSBLs.
UCEPROTECT level 3 lists entire ASN ranges based on aggregated activity from any IP within them; it produces a high false-positive rate and is consulted by very few receivers. Many smaller DNSBLs (anti-spam projects with small operator teams, regional blocklists) appear in our long-tail check but rarely affect production deliverability. A tier-3 listing alone isn't worth aggressive action; most resolve through normal sending pattern continuation without manual intervention.
Multiple listings: read the pattern, not the count.
A single tier-1 listing is more actionable than 10 tier-3 listings. The pattern matters: if you're listed across many tier-1 RBLs simultaneously, the underlying cause is severe and broad; if you're listed at one tier-1 and one tier-3, the tier-3 may be coincidental and the tier-1 is your real problem. Treat the audit as diagnostic information, not a checklist of items to mechanically resolve.
Listings we see most often and what tends to cause them.
Spamhaus SBL: specific snowshoe behavior
Spamhaus SBL listing typically indicates the IP is sending unsolicited bulk mail at volume, usually with patterns matching their snowshoe heuristics (low volume per IP across many IPs, similar content patterns). Fix: audit list quality and acquisition history; identify and remove problematic segments; document remediation; submit delisting with evidence package. Recovery Pack handles this end-to-end.
Spamhaus CSS: subtle compromise indicator
CSS (Composite Spam Sources) is Spamhaus's automated detection of mixed-quality sending patterns. Less severe than SBL but still consulted at major receivers. Often appears before full SBL escalation. Fix: address sending pattern issues quickly to prevent escalation.
Spamhaus PBL: dynamic IP range listing
PBL (Policy Block List) lists IP ranges that should not be sending mail directly to receivers, typically residential ISP ranges. Most legitimate senders are unaffected because they send through dedicated infrastructure. If you appear here, your sending IP is likely on a residential range; you need a proper sending IP from a hosting provider. Not addressable via delisting; requires infrastructure change.
UCEPROTECT level 3: ASN-wide listing
Listed because some IPs in the same ASN have been flagged. Auto-clears in 7 days of clean activity from the ASN; no individual delisting available. Most receivers ignore UCEPROTECT level 3. Generally ignorable unless your specific recipients are using it.
SORBS DUHL: dynamic IP detected
SORBS DUHL lists IPs they classify as dynamic residential. Similar to Spamhaus PBL in that the fix is infrastructure (proper sending IP), not delisting. If your sending IP has been classified as dynamic despite being a static hosted IP, the rDNS and forward DNS may be configured in a way that triggers the classification.
Long-tail listings only (no major RBLs)
Listed at 2-3 smaller blocklists with no Spamhaus, Barracuda, or SORBS listings. Effect on actual deliverability is minimal; these blocklists are consulted by few receivers. Often resolves through time without intervention. Worth monitoring but not urgent.
Why blocklist listings are more damaging than they were two years ago.
The structural impact of blocklist listings has worsened through 2025-2026 even though the listing mechanics themselves have not changed materially. Two specific changes drive most of the worsening.
The first is Gmail moving from soft enforcement to outright SMTP-level rejection in November 2025 for bulk senders (5,000+ daily to personal Gmail accounts) who fail authentication or exceed complaint thresholds. The old behaviour for listed senders was that mail was routed to spam folder where recipients could theoretically retrieve it. The current behaviour returns 550-5.7.26 or 421-4.7.32 rejection codes and the mail never reaches the receiver in any retrievable form. Microsoft completed equivalent enforcement by April 30, 2026.
The second is that ISP-side classification systems rely on longer historical data windows than they did in 2024. Reputation rebuild after a listing now takes 60-120 days on average compared to 30-60 days two years ago. The AI-driven filtering systems weight 60-90 days of trailing signal rather than the 30-day windows that were standard in earlier generations.
The practical implication: pause-and-fix is now structurally more important than it was. Continuing to send while listed under 2026 conditions does not just delay recovery; it actively damages receiver-side reputation that has to be rebuilt separately after the listing clears. The 9-day Spamhaus delisting documented in our affiliate-recovery case study still applies when evidence is properly prepared, but the 60-day reputation rebuild that followed it is now closer to 75-90 days on equivalent infrastructure.
Do not pay anyone for Spamhaus or other blocklist removal.
Spamhaus delisting is free. Barracuda removal is free. SORBS removal is free. UCEPROTECT removal is free (though UCEPROTECT level 3 has historically charged a "fast-track" fee that the community has criticised as effectively extortion-adjacent; the free removal path still works, just takes longer). Every legitimate blocklist offers a free delisting procedure that the network owner or sender can pursue directly.
Any third party offering paid blocklist removal for Spamhaus is operating a scam. Spamhaus has stated this publicly and repeatedly: they have no affiliation with any such service, and no third party can influence or expedite removals from any Spamhaus database. The scam typically targets technically-inexperienced senders who have just been listed and are willing to pay to make the problem disappear.
The cost of professional remediation lies in the audit, the evidence preparation, and the reputation rebuild, not in the delisting submission itself. A vendor that offers "guaranteed delisting in X hours for Y dollars" is either misrepresenting what they do (selling consulting services dressed up as "removal") or directly defrauding the customer. The distinction matters: legitimate consulting helps the sender produce the evidence Spamhaus reviewers need to see. Paid removal services that claim direct influence over Spamhaus are not legitimate.
The same warning applies to most other major blocklists. Senders who receive offers of paid removal from any third party should treat the offer as a red flag about the third party rather than a legitimate service option. Our Blacklist Removal service (€149 in our catalogue) is consulting and evidence preparation; the delisting submission itself is free and we tell customers that openly during scoping conversations.
Frequently asked.
How long does it take to delist from Spamhaus?
Typical timeline 7-21 days from submission, contingent on the evidence package quality. Spamhaus reviewers are responsive when the listing reason is clearly addressed; rejections add days to the cycle. About 75% of properly-prepared submissions clear within first cycle; 20% require additional evidence; 5% require escalation. Self-submitted requests have higher rejection rate due to insufficient evidence preparation.
If I'm listed, will my mail bounce immediately?
Depends on the listing and the receiver. Spamhaus SBL listings typically result in mail going to spam folder at major receivers rather than hard bouncing; some corporate filters do reject SBL-listed mail outright. Barracuda BRBL behaviour varies by filter configuration. UCEPROTECT levels 1-2 cause similar variable behaviour. You may not see hard bounces; you'll see inbox placement collapse instead.
Should I rotate IPs after a listing?
Sometimes. IP rotation is valid when reputation is severely damaged and rebuild on the original IP would take longer than the operational impact can sustain. Rotation is wrong when the underlying cause is sender behaviour; rotating without addressing the cause means the new IP gets listed within weeks. Recovery Pack includes the judgment call: we recommend rotation when it's the right answer, retain the IP when rebuild is preferable.
Can my domain be listed even if my IPs are clean?
Yes. Spamhaus DBL and SURBL list domains based on content classifier signals or domain-level reputation, independent of sending IP. Domain listing is sometimes harder to address than IP listing because the cause is often content patterns rather than infrastructure.
How often should I check?
Daily monitoring is appropriate for production sending operations. Manual check is reasonable weekly for lower-volume operations. We provide Deliverability Monitoring service for continuous 15-minute granularity tracking with alerts when listings appear.
The check shows clean but my mail goes to spam. Why?
Blocklist status is one of many signals receivers use; clean RBL status doesn't guarantee inbox placement. Other factors: content classifier, sender reputation accumulated at the receiver level (not visible via public RBLs), recipient engagement patterns, authentication alignment. Use SPF/DKIM/DMARC validator for authentication checks; Deliverability Audit covers full diagnosis.