DNS blocklist monitoring now available to all Oh Dear users
Published on February 23, 2026 by Mattias Geniar
Your domain is on a spam blocklist. Password reset emails aren't arriving, order confirmations land in spam, and customers are complaining that "your site doesn't work." By the time you hear about it, the damage has been building for days.
We've shipped DNS blocklist monitoring to catch this early. Oh Dear now checks your domain against 11 major blocklists and notifies you the moment you're listed, with direct links to get removed.
Two kinds of blocklists, two kinds of pain #
Not all blocklists are the same. We monitor two categories:
Security blocklists (RBLs) are the ones that wreck your email deliverability. If your IP or domain appears on Barracuda, SpamCop, SURBL, or URLhaus, email servers will reject or spam-folder your messages. Password resets, order confirmations, support replies: silently gone.
Content filter DNS services block your site entirely for users behind DNS-level filtering. If Quad9, Cloudflare Family, AdGuard, or OpenDNS blocks your domain, anyone using those services (directly, or through tools like Pi-hole and AdGuard Home) simply can't reach you. That's millions of privacy-conscious users, corporate networks, and families with parental controls.
The 11 blocklists we check #
| Category | Provider | What it catches |
|---|---|---|
| Security | Barracuda | IP reputation |
| Security | SpamCop | Real-time spam reports |
| Security | SURBL | Spam, phishing, malware domains |
| Security | URLhaus | Malware distribution URLs |
| Content filter | AdGuard DNS | Ads, trackers, malware |
| Content filter | AdGuard Family | Ads, trackers, adult content |
| Content filter | CleanBrowsing | Malware and phishing |
| Content filter | Cloudflare Family | Malware and adult content |
| Content filter | OpenDNS | Malware and phishing |
| Content filter | OpenDNS Family | Malware, phishing, adult content |
| Content filter | Quad9 | Malware and phishing |
How it works #
For security blocklists, we perform standard DNSBL lookups. IP-based lists like Barracuda get a reversed-IP query against their DNS zone. Domain-based lists like SURBL get a direct domain query. A DNS response means you're listed.
For content filter services, we resolve your domain through each provider's DNS server. If the response is NXDOMAIN or a known block-page IP (like 0.0.0.0 for AdGuard), your domain is blocked by that service.
Checks run daily by default. You can increase the frequency to every 4 hours if you want tighter coverage, or pick specific blocklists instead of monitoring all 11.
What happens when you're listed #
You get a notification through whichever channels you've configured: email, Slack, Discord, Teams, Telegram, PagerDuty, Opsgenie, Pushover, SMS, webhooks, ntfy, or Google Chat.
The notification tells you exactly which blocklist flagged you and why. Your dashboard shows direct links to each provider's delisting form, so you can start the removal process immediately instead of researching where to go. All the info you need, at your fingertips.
When you're removed from all blocklists, you'll get a recovery notification confirming the all-clear.
If you're working on a fix and don't want repeated alerts, you can snooze the check.
It's probably not your fault #
Domains get blacklisted for reasons beyond your control:
- Shared hosting: a neighbor on your IP sends spam, your IP gets flagged
- Domain history: you registered a domain previously owned by bad actors
- IP history: you provisioned a new VM and got an IP that was previously abusive
- Compromised sites: attackers inject content you don't even know about
- Email misconfiguration: missing SPF/DKIM records or an open relay
Regardless of the cause, you need to know fast. The longer you stay listed, the more damage accumulates.
API access #
DNS Blocklist history is also available through our API. Fetch all check results for a monitor:
GET /api/monitors/{id}/dns-blocklist-history-items
Each result includes the checked domain, resolved IPs, and per-provider results with listing status, return codes, and reasons. Full details in our API documentation, or use our PHP-SDK for convenience.
Ready to be enabled by everyone #
DNS blocklist monitoring is available for all monitors. Head to your monitor's settings, enable the DNS Blocklist check, and you're covered. All 11 blocklists are monitored by default.
Read the full documentation for configuration options and remediation guides.
Want to bulk-update this check for all your monitors? Just reach out via support.
