The short answer
BlacklistMonitoring has a REST API for blacklist checks and blacklist monitoring on the Scale plan. You send a domain, an IP or an IPv4 range, we check it on 109 IP and domain blacklists every 5 minutes, and your systems read open listings over the API or receive them as HMAC signed webhooks. Scale costs $1,499 a month, or $749 a month billed yearly, and covers 5,000 domains and IPs.
It is built for teams that own a lot of sending infrastructure and need listings inside their own tools: hosting providers and MSPs watching customer ranges, email service providers watching shared pools, and agencies that open a ticket for the right client automatically. If you only need to look up a handful of addresses now and then, the IP blacklist checker on this site does that without a token.
What the blacklist API does
Authentication is a bearer token scoped to one workspace, created and revoked under API in your workspace settings. The limit is 120 requests a minute per token and 1,000,000 requests a month on Scale. Full request and response examples are in the API reference.
| Endpoint | What it returns |
|---|---|
| GET /api/v1/assets | Every domain, IP and range in the workspace with its score and listed count. Filter by tag or by status=listed. |
| POST /api/v1/assets | Adds a domain, a single IP or a CIDR range with an optional label and up to 20 tags. |
| GET /api/v1/assets/{id} | One asset, its latest check (lists checked, listed count, errors) and every open listing. |
| POST /api/v1/assets/{id}/check | Queues a re-check now, outside the 5 minute schedule. Returns a check id. |
| GET /api/v1/listings | Open listings across the workspace, or all listings within your history window, with list name, DNS zone, return code, its meaning and the removal URL. |
| GET /api/v1/assets/{id}/findings | SPF, DKIM, DMARC, MX and PTR findings with severity, a code and the fix. |
| Webhooks | listing.opened, listing.closed, finding.opened and finding.resolved as JSON POSTs, signed with an X-Signature HMAC SHA-256 header. |
Why a monitoring API beats calling a lookup API in a loop
- You stop paying for clean answers. Most blacklist check APIs bill per lookup, and 99 percent of lookups come back clean. With monitoring, the checking happens on our side and your code only hears about the listings that matter.
- Push instead of poll. A webhook lands within minutes of a listing. A cron job that loops over 2,000 IPs once an hour finds the same listing up to 60 minutes later and burns quota every time it runs.
- The removal link comes with the alert. Every listing carries the return code, what that code means on that list and the delisting page, so the ticket your system opens already says what to do next.
- Whole ranges, not single IPs. On Scale you add 198.51.100.0/24 once and every address in it is watched. Hosting and MSP teams no longer need to keep a separate spreadsheet of tenant IPs in sync.
- The cause is in the same API. Findings flag the SPF, DKIM or DMARC change that usually comes before a listing, so a broken signing key shows up before the blocklists do.
Blacklist check API pricing compared
Competitor figures come from each vendor's public pricing and API pages and can change, so confirm them before you sign. If your use is a few thousand ad hoc lookups a month, a per-call plan from BlacklistMaster costs less than ours. If you need 5 minute coverage of thousands of sending IPs plus authentication checks and a webhook into your ticketing system, Scale replaces the lookup loop, the monitor and the DMARC tool at once. See every plan on the pricing page.
| BlacklistMonitoring Scale | HetrixTools | BlacklistMaster | MxToolbox | |
|---|---|---|---|---|
| API access | Scale plan | Every plan, including Free | Separate API plans, or with monitoring plans | Free lookup allowance, more on paid plans |
| Published price | $1,499/mo, $749/mo billed yearly | $9.95 to $99.95/mo | $10/mo for 10,000 calls up to $900/mo for 2,000,000 | Not published for the API, quote on request |
| Model | Monitoring with push webhooks | Monitoring with API and alerts | Per-call lookups plus monitors | Lookups and monitors |
| Fastest check interval | Every 5 minutes | Every 2 hours on Business and Enterprise | Every 20 minutes on Premium | Depends on plan |
| Blacklists | 109 IP and domain lists | 94 plus Microsoft SNDS | See vendor site | See vendor site |
| CIDR ranges | Yes | Yes | Single IPs and domains | See vendor site |
| SPF, DKIM, DMARC findings | Yes, plus DMARC report parsing | No | No | Separate tools |
| Where they win | Price, monitor counts, uptime in the same account | Cheapest for occasional per-call lookups | Brand recognition, wide free toolset |
Who uses the blacklist monitoring API
- Hosting providers and MSPs. Add each customer range with a tag, and route listing.opened webhooks to the account owner so an abusive tenant is found the same hour.
- Email service providers. Watch shared and dedicated pools, pull the open listings into your own status page and move traffic off a listed IP before customer complaints start.
- Cold email and marketing agencies. Add every new sending domain from your onboarding script and open a client ticket automatically. Our deliverability monitoring for cold email agencies page covers the workflow.
- Security and IT teams. Feed listings and findings into a SIEM or on-call tool next to your other alerts, using the same IP blacklist monitoring data the dashboard shows.
How to start with the API
- 1 Create your account and pick the Scale plan, monthly or yearly.
- 2 Open API in your workspace settings, create a token and store it in your secrets manager.
- 3 POST your domains, IPs and CIDR ranges to /api/v1/assets, with tags for customer or pool.
- 4 Add a webhook channel with a secret and verify the X-Signature header on each request.
- 5 Read GET /api/v1/listings?status=open once to backfill, then let webhooks drive your tickets.
Frequently asked questions
Is there an API for blacklist checks?
Yes. BlacklistMonitoring has a REST API on the Scale plan that adds domains, IPs and CIDR ranges, checks them on 109 blacklists every 5 minutes, returns open listings with return codes and removal links, and pushes signed webhooks. HetrixTools, BlacklistMaster and MxToolbox also offer blacklist APIs with different pricing models.
How much does a blacklist check API cost?
It depends on the model. Per-call lookup APIs start around $10 a month for 10,000 calls at BlacklistMaster. Monitoring plans with API access run from $9.95 a month at HetrixTools to $1,499 a month ($749 billed yearly) for our Scale plan, which adds 5 minute checks, CIDR ranges and DMARC data.
How do I check if an IP is blacklisted programmatically?
Add the IP to a workspace with POST /api/v1/assets, then read GET /api/v1/assets/{id}, which returns the latest check and every open listing. For instant results, call POST /api/v1/assets/{id}/check. Most teams skip polling and act on the listing.opened webhook instead.
Can I monitor whole IP ranges over the API?
Yes. On Scale you can add an IPv4 CIDR range such as a /24 as one asset, and every address in it is checked on the same schedule. Listings come back per IP, so you can map them to the customer or pool that owns that address.
What rate limits does the API have?
Each token can make 120 requests a minute. Requests over that get HTTP 429 with a Retry-After header. Scale includes 1,000,000 API requests a month, and on-demand re-checks are separate from the scheduled 5 minute checks, which always run.
Do I need the API to get webhooks?
No. Signed webhooks for listings and findings are available from the Business plan at $149 a month. The REST API on Scale adds the ability to add and remove assets from your own code and to read listings and findings on demand.