--- title: Blacklist Monitoring for Mail Server IPs description: Blacklist monitoring by WatchFor. Check your mail server's IP against Spamhaus ZEN, Barracuda and SpamCop, or the DNS blocklists you choose, every hour, and get alerted when it's listed. canonical: https://watchfor.io/blacklist-monitoring --- # Blacklist Monitoring for Mail Server IPs Find out when your mail server's IP lands on Spamhaus, SpamCop or another DNS blocklist, so you can fix the cause and request delisting before mail bounces. [Get started for free](/auth/sign-up)[View pricing](/pricing) [Email round-trip monitoring](/email-round-trip-monitoring)[SMTP monitoring](/smtp-monitoring) ## Blacklist Monitoring Features What each check looks up, and how it decides ### Default Blocklists, or Your Own Every check queries Spamhaus ZEN, Barracuda and SpamCop by default. Replace them with the DNSBL zones that matter to you, one per line, such as UCEPROTECT or a regional list. ### IP-Based Lookups Lists are checked with a reverse-IP lookup on your server's IPv4 address. Enter the IP, or the mail server's host name and the monitor resolves it; domain blocklists and IPv6 aren't supported. ### Listing Alerts Listed on Any RBL is on by default at critical severity. Listed on Multiple RBLs and High RBL Failure Rate are there when you want them, and alerts go to your usual channels. ### Per-List Visibility See which blocklists flagged you, which came back clean and how long each lookup took, so you know how serious a listing is and where to file a delisting request. ### Failed Isn't Listed A list that times out or refuses the query shows as failed, not listed, so a resolver problem never looks like a listing. High RBL Failure Rate tells you when too many lists stop answering. ### A Resolver That Gets Answers Spamhaus refuses queries from public resolvers, so lookups go through our own resolver by default. Set a custom resolver if you use a Spamhaus DQS key or a list that needs one. ### Listing History Each check stores the verdict and lookup time for every list, and incidents show when a listing started and when it cleared. ### Hourly Checks Checks run as often as every hour. A listing needs 3 checks in a row to open an incident by default, adjustable down to 1; this type skips fast re-checks because lists are rate-limited. ## A closer look Alert on one listing, on several, or when the lists stop giving a verdict. Each check records the verdict and lookup time for every RBL you choose. ## Why Choose Our Blacklist Monitoring Solution? A single blacklisting can quietly wreck your email deliverability: messages land in spam or get rejected outright, and the damage to your sending reputation can linger for days. Our monitoring checks your mail server's IP against the blocklists you choose every hour and tells you when a new listing appears. The per-list table names the list that flagged you, so you know where to request delisting, and the incident resolves on its own once the listing clears. [Start monitoring now](/auth/sign-up) Check any mail server IPv4 address, or a host name that resolves to one Spamhaus ZEN, Barracuda and SpamCop by default Add any DNSBL zone, one per line Per-list results so you know exactly who flagged you Timeouts and refusals kept apart from real listings Custom resolver for a Spamhaus DQS key Hourly checks on the Starter plan and above Alerts on any of 16 channels, including email, Slack and PagerDuty ## How Blacklist Monitoring Works From IP to alert in four steps 1 ### Add Your Mail Server Enter the sending IP address, or the mail server's host name. Add one monitor for each IP you send from; the REST API helps when there are many. 2 ### Choose Your Lists Keep the three default blocklists or enter your own, pick how often to check and which channels should receive alerts. 3 ### Monitor 24/7 Each check queries every list for your IP and records which ones flag you, which stay clean and which fail to answer. 4 ### Get Alerts When a listing is confirmed, you're notified on your channels with the list that flagged you, and the incident resolves once you're delisted. ## Blacklist Monitoring Use Cases Essential for anyone whose business depends on email ### Transactional Email Password resets, receipts and confirmations have to arrive. A blacklisting can send these messages straight to spam, so catching a listing early keeps your core flows working. ### Marketing & Newsletters Campaign performance collapses when your sending IP gets blocklisted. Monitoring protects open rates and revenue by alerting you before a listing ruins an entire send. ### Self-Hosted Mail Servers Running your own mail infrastructure means you own its reputation. Regular blacklist checks let you spot a compromised or misconfigured server before providers start rejecting your mail. ### Shared & Cloud IPs On shared sending infrastructure, a noisy neighbour can get the whole range listed. Monitoring tells you once the listing is confirmed, so you can react, escalate or move to a clean address. ## Frequently asked questions Everything you need to know about blacklist monitoring [All questions→](/faq)[Ask us directly](/contact) What is blacklist (DNSBL/RBL) monitoring? Blacklist monitoring checks whether your mail server's IP address appears on DNS-based blocklists, also called DNSBLs or RBLs. Mail providers consult these lists to decide whether to accept, spam-folder or reject your mail. Monitoring them means you hear about a listing from an alert, not from bounced messages days later. How does blacklist monitoring work? Why does getting blacklisted matter? Which blacklists do you check? How do I get removed from a blacklist? Can I monitor both IP addresses and domains? How often are blacklist checks performed? What happens when a new listing is detected? Why does a list show as failed instead of clean? ## From our blog Guides, deep-dives, and best practices from the WatchFor team [Email ### Email Blacklists (RBLs): why you're blocked and how to get off Mar 25, 2026·3 min readRead article](/blog/email-blacklists-rbl)[Email ### Why Your Emails Go to Spam (and how to fix it) Dec 02, 2025·3 min readRead article](/blog/why-emails-go-to-spam)[Email ### Email Authentication Explained: SPF, DKIM & DMARC Apr 25, 2026·4 min readRead article](/blog/spf-dkim-dmarc-explained) ## Ready to Protect Your Email Deliverability? Blacklist monitors are included from the Starter plan. Run the free blacklist checker first, or sign up for free and upgrade when you add your first mail server. [Get started for free](/auth/sign-up)[View documentation](/docs/monitors/security#blacklist-rbl) --- Canonical page: https://watchfor.io/blacklist-monitoring · Site guide: https://watchfor.io/llms.txt