Watch DNS blacklists (DNSBL monitor)

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The DNSBL monitor (API type dnsbl, shown in the app as DNSBL check) looks your domain’s addresses up in DNS-based blacklists (DNSBLs) and alerts you when one of them lists you. A listing quietly sends your email to spam folders and can get your site flagged by security software - usually long before anyone tells you.

At a glance


API type token	`dnsbl`
Runs from	HostTracker’s own internal check network - no location picker
Schedule	every 6 hours, fixed
Plan gates	the DNSBL type is a package feature (`dnsbl`)

How it decides

Each check resolves the addresses in scope and queries them against HostTracker’s catalogue of blacklists.

Down when the address is listed on any blacklist that counts (the catalogue weights each list; listings on minor lists and listings you muted are shown but do not count). The alert names the lists.
Down when the domain does not exist in DNS at all.
An IPv6-only host cannot be tested by IPv4 blacklists; the check stays Up and notes that.
If some blacklists do not answer, the check concludes on the ones that did; if none answer, it tries again at the next run instead of guessing.

Settings reference

The name, tags, Full Log, Open Stats and subscriptions work as described in Common monitor fields.

Setting (app label)	API field	Type / allowed values	Default	Plan limits	What it does for you
Domain / IP	`url`	domain or IP	required	-	What to check.
What to check (Check Configuration)	`settings.scope`	`firstWebIp` (Web address IP), `allWebIps` (All web IPs), `webAndMx` (Web + mail (MX))	`firstWebIp`	-	Only the first A record, every A record, or every A record plus the IPs of your MX mail servers - the ones spam filters look up.
Interval	`interval`	ignored	6 hours	-	Fixed; a sent value is replaced and the response carries a warning. Cron is not supported.
Locations	`locations`	not accepted	-	-	Sending pools is refused.

When you change only url in an update, the stored scope is kept.

Blacklist status and muting

In the editor, Blacklist status lists every current listing: Blacklist, Listed endpoint, a Note from the list, a MAJOR marker for significant lists, a Delist link to the list’s removal page, and Mute / Unmute. A muted listing stays visible but no longer turns the monitor Down - use it for a list you have decided to ignore.

Set it up in the app

On the Sites dashboard, click Add Monitor and choose DNSBL check in Monitoring Type.
Enter the domain or IP in Domain / IP and a name.
In Check Configuration, choose What to check - Web + mail (MX) when email reputation matters.
Click Save. After the first check, open the monitor to see Blacklist status.

Do it with the API or MCP

curl -X POST https://api2.host-tracker.com/monitor \
  -H "Authorization: Bearer $HT_TOKEN" -H "Content-Type: application/json" \
  -d '{ "type": "dnsbl", "url": "example.com", "settings": { "scope": "webAndMx" } }'

Update the scope:

curl -X PATCH https://api2.host-tracker.com/monitor/<monitor-id> \
  -H "Authorization: Bearer $HT_TOKEN" -H "Content-Type: application/json" \
  -d '{ "settings": { "scope": "allWebIps" } }'

Read the listings with GET /monitor/{monitorId}/attached (the dnsbl block: listings[] with name, host, txt, weight, removalUrl, muted, plus checkedAt), and mute or unmute with:

curl -X POST https://api2.host-tracker.com/monitor/<monitor-id>/attached/dnsbl/mute \
  -H "Authorization: Bearer $HT_TOKEN" -H "Content-Type: application/json" \
  -d '{ "listings": ["<blacklist name>"], "muted": true }'

MCP: create_monitor(type="dnsbl", url="example.com", settingsJson="{\"scope\":\"webAndMx\"}") - no interval, no pools. Read listings with get_monitor(id, expand="attached").

Recipes

Mail deliverability - scope webAndMx on your mail domain.
A server with several addresses - scope allWebIps.
A shared-hosting IP - put the IP itself in url.

What happens next

The first check runs shortly after you save, then every 6 hours. A new listing turns the monitor Down and alerts the subscribed contacts; a still-listed monitor repeats the reminder at most once a day. Delisting is done on the blacklist’s own site (the Delist link); the monitor turns Up at the next check after the list drops you.

Limits and gotchas

The address must not contain !## (422 invalid_settings).
403 package_limit - your package does not include DNSBL monitors.
422 validation_failed with reason: pool_not_supported_for_type - omit locations.
HostTracker checks DNS blacklists only. It does not monitor SPF, DKIM, DMARC or email delivery.