How to Check if Your IP is Blacklisted (and What to Do)

Your emails disappear. Your web requests get blocked. Your ad campaigns tank for no obvious reason. Sometimes the culprit is invisible: your IP address is on a blacklist, and the internet is quietly treating you like a spammer.

What a Blacklist Actually Is

IP blacklists — also called blocklists or DNSBLs — are databases of IP addresses associated with spam, malware, phishing, or other abuse. Email servers, firewalls, and ad networks query these lists to decide whether to accept traffic from a given IP. There are over 100 active blacklists, maintained by different organisations with different standards for getting listed and getting off.

The big ones are Spamhaus, Barracuda, and SORBS. Getting listed on Spamhaus alone will cause your emails to bounce at roughly 40% of corporate mail servers. It's not a light problem.

Why Legitimate IPs Get Blacklisted

Here's the thing — you don't have to be a spammer to end up on a blacklist. Shared hosting means your IP might have been used by a different account before you. A malware infection on your network can turn your devices into spam-sending zombies without you knowing. ISPs sometimes allocate previously abused IP ranges to new customers. And dynamic IP addresses that were once used by bad actors get flagged before they're recycled.

One of the most common routes is a compromised WordPress site. A single injected script sending 3,000 spam emails per hour is enough to land you on Spamhaus within 48 minutes — and it happened on a small UK hosting account a few years back, earning the owner a three-week delisting battle.

How to Check Your Status

Run your IP through a multi-blacklist checker — tools like MXToolbox or our own blacklist checker query dozens of lists simultaneously. Look at which specific lists flagged you, because the delisting process is different for each one. Spamhaus has a self-service lookup. Barracuda has a removal request form. Some smaller lists require direct contact.

Getting Delisted

Before requesting removal, fix the underlying problem. Delisting a still-abusing IP is pointless — you'll be back on within days. Scan your network for malware (using reliable network tools to audit open connections), audit your email sending practices, and check whether any scripts or applications are generating unusual outbound traffic. Then submit your removal request with evidence of the steps you've taken.

That said — some lists delist automatically after 30 days of clean behaviour. If you're in a hurry, the paid express removal options from some providers are legitimate and worth it for business-critical situations.

After Delisting: Monitoring Going Forward

Getting off a blacklist is only half the job. Without monitoring, you'll find out about re-listing the same way you found out the first time — when something breaks. Set up regular blacklist checks on your IP as a scheduled task. MXToolbox offers free monitoring with email alerts. If you're running an email server, watch your bounce rates — a sudden spike in 5xx rejections is often the first sign of a new listing before you've checked manually.

DMARC reporting is worth setting up even for small senders. It gives you a daily XML digest of every email claiming to be from your domain, who sent it, and whether SPF/DKIM passed. Attackers who spoof your domain to send phishing emails can get your domain's reputation damaged in spam filters even if your IP is clean. DMARC catches that — or rather, it tells you it's happening, which is the first step to stopping it.