# DNS blocklist monitoring If your domain ends up on a blocklist, your emails land in spam folders and your website becomes unreachable for millions of users with ad-blockers. Most teams discover they're blacklisted weeks later - from customers complaining emails never arrived or reports that the site "doesn't work." We check 11 major blocklists every few hours. The moment you're listed, you'll know - with clear guidance on how to get removed. [ Start monitoring ](https://ohdear.app/register) 10 day free trial No credit card required ## Email deliverability disasters When your emails silently disappear Password reset emails never arrive - customers are locked out of their accounts and your support team is overwhelmed. Order confirmations go to spam - customers think their orders failed and place duplicates or abandon your store entirely. Marketing campaigns have near-zero open rates. You've spent weeks crafting the perfect email, only to have it filtered into spam folders across Gmail, Outlook, and corporate email systems. Revenue lost, effort wasted. Support ticket responses never reach customers. They're waiting for help, getting increasingly frustrated, while your replies sit in their spam folder. Your support metrics tank, customers churn. We check the major email blocklists: **Barracuda** (widely used by enterprises), **SpamCop** (real-time spam reporting), **SURBL** (multi-source domain list), and **URLhaus** (malware URLs). What a blacklisting breaks Password resets never arrive Order confirmations marked spam Site blocked for DNS filter users Customer support breaks down ## Blocked by ad-blockers and DNS filters Millions of users can't reach your site Tools like Pi-hole, AdGuard Home, and NextDNS let users run DNS-level filtering on their network. These tools often use the same upstream DNS services we monitor (Quad9, OpenDNS, Cloudflare Family, AdGuard DNS) as their resolvers. If your domain is blocked by one of these services, anyone using them directly or through a tool like Pi-hole won't be able to reach your site. Corporate networks using OpenDNS or Cloudflare Family protection deny access to your site. Employees trying to access your service from work? Blocked. Potential customers researching your product during office hours? Can't reach you. We check the major content filter DNS services: **AdGuard DNS** (ads and malware), **AdGuard Family** (adult content), **CleanBrowsing** (security), **Cloudflare Family**, **OpenDNS**, and **Quad9**. ## Why domains get blacklisted It's not always your fault **Shared hosting:** Another site on your IP sends spam. You've done nothing wrong, but your IP address gets blacklisted because a neighbor on the same server was sending spam. Suddenly your emails bounce too. **Compromised website:** Attackers inject malicious content or use your site for phishing. Security scanners detect it and add your domain to blocklists. You might not even know you were compromised. **Misconfigured email server:** An open relay, missing SPF/DKIM records, or overly aggressive marketing emails can get your domain flagged as a spam source. **Domain history:** You registered a domain that was previously owned by bad actors. Their reputation follows the domain, not the owner. You inherit their blocklist entries. Regardless of the cause, you need to know immediately so you can take action. ## Clear path to removal Detection plus remediation guidance **Immediate notification when listed.** The moment we detect your domain on any of our monitored blocklists, you'll receive an alert through your preferred notification channels. **Which specific blocklist flagged you.** Not all blocklists are equal. We tell you exactly which list has your domain, what type of content or behavior it blocks, and how widely that list is used. **Direct links to removal request forms.** Each blocklist has its own delisting process. We provide direct links to the relevant removal request pages, saving you the research time. **Snooze when you need to.** Working on a fix and don't want to keep getting alerts? You can snooze the entire DNS blocklist check for a set period, so you won't be disturbed while resolving the issue. ## Who needs blocklist monitoring? Anyone who sends email or cares about reachability **E-commerce businesses** where transactional emails are critical. Order confirmations, shipping notifications, password resets - if these don't arrive, customers lose trust and you lose sales. **SaaS companies** where user onboarding depends on email. Verification emails, password resets, team invitations - if your domain is blacklisted, new users can't even get started. **Marketing teams** whose campaign success depends on deliverability. Before launching that big campaign, make sure you're not already on a blocklist that will tank your open rates. **Anyone with customers using ad-blockers.** Tech-savvy users, developers, privacy-conscious consumers - a significant portion of your audience may use DNS-based ad blocking. If you're blocked, they simply can't reach you. **Companies with online reputation to protect.** Being on a blocklist signals to potential customers that your domain might be unsafe. Protect your brand by staying off these lists. ## Stop worrying, start monitoring Start a no-strings-attached 10-day free trial. You're all set in less than a minute. (No credit card needed.) Not convinced yet? Need help? Get in touch via . ## The blocklists we check 11 lists covering email and content filtering **Email/Spam blocklists (4 lists):** - **Barracuda** - Widely used by enterprises - **SpamCop** - Real-time spam reporting network - **SURBL** - Multi-source domain blocklist - **URLhaus** - Malware URL database **Content filter DNS services (7 lists):** - **AdGuard DNS & Family** - Blocks ads, trackers, adult content - **CleanBrowsing Security** - Blocks malware and phishing - **Cloudflare Family** - Blocks malware and adult content - **OpenDNS & Family** - Enterprise and family protection - **Quad9** - Security-focused DNS We maintain these lists continuously. When new blocklists gain adoption or existing ones change, we update automatically - you don't have to do anything. ## Really into the nitty gritty details? Want to get into the nitty gritty details of our monitoring? Have a look at our documentation. ## Frequently asked questions ### What is DNS blocklist monitoring? It checks whether your domain and its IP addresses have landed on DNS blocklists, the spam and content-filter lists that mail servers and DNS resolvers use to decide what to block. Get listed and your email starts bouncing or your site gets filtered, usually without any warning. ### Which blocklists does Oh Dear check, and how often? We check your domain and IPs against a range of email and content-filter blocklists every few hours, covering the spam lists that hurt email deliverability and the DNS filters (like the ones AdGuard, Cloudflare, OpenDNS, and Quad9 run) that can block your site outright. ### Will I know the moment I get listed or delisted? Yes. Oh Dear alerts you when your domain or IP appears on a blocklist, tells you exactly which one flagged you, and lets you know again once you're delisted. You can snooze a listing you're already working on. [See all other FAQ items →](https://ohdear.app/docs/faq) ## Start monitoring instantly Start a no-strings-attached 10-day free trial. You're all set in less than a minute. (No credit card needed.) Not convinced yet? Need help? Get in touch via .