Blacklist Monitoring
Continuous checks of your domain and IP against 20 major RBLs, with honest guidance on which listings actually matter.
Blacklist monitoring checks your domain and sending IP against 20 real-time blackhole lists (RBLs). Each check returns listed or clean per list, and new listings fire a blacklist.listed notification — plus a webhook event if you've configured one.
The 20 lists
| List | Type |
|---|---|
| Spamhaus (SBL/XBL/PBL) | IP and domain reputation |
| Barracuda | IP reputation |
| SpamCop | IP reputation (complaint-driven) |
| SORBS | IP reputation |
| URIBL | Domain/URI reputation |
| SURBL | Domain/URI reputation |
| Invaluement | IP and domain reputation |
| Proofpoint | IP reputation |
| CBL/Abuseat | Compromised-host detection |
| SenderScore | IP reputation scoring |
| TrendMicro | IP reputation |
| McAfee | IP reputation |
| Abusix | IP reputation |
| JunkEmailFilter | IP reputation |
| PSBL | Passive spam trap list |
| HostKarma | IP reputation |
| GBUdb Truncate | IP reputation |
| WPBL | IP reputation |
Which lists actually matter
Honest answer: not all 20 are equal. A few are consulted directly by major mail providers and enterprise filters; many are informational and have little or no measurable effect on delivery.
- High impact: Spamhaus is the most widely enforced list in the world — a Spamhaus listing will block delivery at a large share of receivers. Barracuda and SpamCop are also used by real filtering products at scale.
- Moderate impact: Invaluement, Proofpoint, SURBL, and URIBL feed commercial filters, so a listing there can affect delivery to organizations running those products.
- Mostly informational: Lists like SORBS, PSBL, HostKarma, WPBL, and GBUdb are aggressive or narrowly scoped, and few major receivers enforce them. A listing there is worth noting, rarely worth panicking over.
If you're clean on Spamhaus, Barracuda, and SpamCop but listed on one obscure aggregator, and your placement tests still show inbox delivery, your deliverability is fine. Fix the listing when convenient — don't treat it as an incident.
What to do when you're listed
- Confirm the impact. Run a placement test (see Placement Tests quotas on pricing) — if mail still inboxes, the listing isn't being enforced against you yet.
- Find the cause before delisting. Common causes: a bounce spike from a stale list, a compromised mailbox sending spam, a shared IP neighbor, or hitting a spam trap. Delisting without fixing the cause gets you relisted within days.
- Follow the delisting guidance. Each listed result includes guidance for that specific list. Most RBLs offer a self-service delisting form; Spamhaus requires you to identify and resolve the underlying issue first; SpamCop listings often expire on their own within 24–48 hours once the spam stops.
- Re-check. Monitoring will show the list flipping back to clean once the delisting processes.
Prevention beats delisting. Gradual volume ramp via warmup, clean recipient lists, and healthy authentication (verify with the free DNS checker) keep you off these lists in the first place. Watch your bounce rate — it's the most common precursor to a listing.
Blacklist monitoring with the full 20-list coverage is included on Starter and Pro plans; see pricing for details.