How to check if your IP is blacklisted (and fix it)

Quick answer

If your emails are bouncing, your messages land in spam, or a service suddenly blocks you, your IP address may be on a blocklist (also called a DNSBL or RBL — a DNS-based blocklist). Mail servers and security systems consult these lists to decide whether to trust traffic from an address. Here’s how to find out and what to do about it.

Step 1: Check your IP against the major lists

The fastest way is our Blacklist Check tool, which queries the blocklists mail servers actually consult — Spamhaus, SpamCop, Barracuda, SORBS and others — in one pass. Leave the field blank to check the IP you’re connecting from, or paste a specific server IP. A “listed” result on any of them is worth investigating.

One honest caveat: blocklists rate-limit lookups from shared resolvers, so a “clean” result here is indicative, not an absolute guarantee of deliverability. If email is still failing despite a clean check, the listing may be on a list that didn’t answer, or the problem may be authentication (SPF/DKIM/DMARC) rather than reputation.

Step 2: Find out why you’re listed

Each blocklist publishes a lookup page that explains why an IP is listed. Spamhaus, for example, tells you whether the listing is for spam output, a compromised machine, or a policy block (like a residential IP sending mail directly). The reason determines the fix — you can’t resolve a listing without addressing its cause first.

Step 3: Fix the underlying cause

Common causes and fixes: a compromised device or account sending spam (find and clean it, reset credentials); an open relay or misconfigured mail server (lock it down); or sending bulk mail from a residential connection (use a proper relay or transactional email service instead). Removing the listing without fixing the cause just gets you re-listed.

Step 4: Request delisting

Once the cause is resolved, use each list’s removal form. Many lists auto-expire clean IPs after a set period; others require a manual request. Provide the IP and, if asked, a brief note on what you fixed. Delisting can take from minutes to a couple of days to propagate.

What if it’s a shared or residential IP?

If you’re on a shared hosting IP or a residential connection behind CGNAT, a neighbour’s behaviour can get the shared address listed through no fault of yours. In that case, contact your host or ISP — you usually can’t delist an address you don’t control. See our related guide on IP reputation on shared hosting.