Blocklist Check
Check an IP or host against additional blocklists.
Enter a value above to run Blocklist Check
e.g. 1.2.3.4
Quick answer
Blocklist Check queries an IP or host against additional reputation blocklists beyond the standard set, catching sources tied to spam, botnets, or malicious activity. A clean result means none of these lists flagged the address.
Blocklist Check queries an IP address or hostname against additional reputation and blocklist sources beyond the common mail DNSBLs. It exists because IPs get flagged for many reasons: spam, malware distribution, compromised hosts acting as proxies, brute-force scanners, or shared hosting neighbors who abused the address before you. Any single listing can quietly break outbound mail, trip firewalls, or get your traffic challenged. This tool gives you one place to see whether a given address is currently listed, so you can confirm a problem, gather evidence, and start a delisting request.
How it works
You enter an IPv4 or IPv6 address, or a hostname that resolves to one. The tool checks that target against a set of blocklist and reputation feeds, each of which maintains its own criteria for adding an entry. For each source it reports whether the address is listed and, where available, a reason or reference link. Because listings are cached and refreshed on different schedules, results reflect each provider's most recent view rather than a single global verdict.
How to read the results
A "not listed" result across every source is the clean outcome you want. A hit on one or more lists means that provider considers the address a risk. Note which list flagged you and why: policy lists (dynamic IP ranges, missing rDNS) differ from abuse lists (observed spam or attacks). Recent, active listings hurt deliverability most; stale entries on minor lists rarely matter. Use the reference link on each listing to reach that operator's delisting or evidence page.
Common problems & fixes
If you are listed, first stop the behavior that caused it: patch a compromised box, close an open relay, fix a spam-sending script, or secure leaked credentials. Only then request delisting, since premature requests fail and can extend cooldowns. For a newly assigned IP inheriting a previous tenant's reputation, provide that context. Make sure the host has valid reverse DNS, SPF, DKIM, and DMARC before assuming the blocklist itself is the whole story.
Frequently asked questions
- How is this different from a standard DNSBL lookup?
- A standard DNSBL check usually queries the well-known anti-spam zones like Spamhaus or SORBS. This tool adds further reputation and blocklist sources so you catch listings those big three might miss, including feeds focused on scanning, malware, and abuse rather than only bulk email. It gives a broader picture of how different operators currently rate the address.
- I am listed but I never sent spam. Why?
- Common causes are a compromised device on your network sending traffic without your knowledge, a shared or recycled IP whose previous owner was flagged, a misconfigured mail server acting as an open relay, or automated scanning from your address. Some lists also flag entire dynamic or datacenter ranges by policy, regardless of your individual behavior.
- How long does delisting take once I fix the problem?
- It varies by operator. Some lists expire entries automatically after a quiet period of hours or days once the abusive traffic stops. Others require a manual removal request and may hold a short cooldown to confirm the issue is resolved. Re-run this check afterward to verify the address has actually cleared before assuming mail flow is restored.