How do you check if your domain or IP is listed?

You notice your open rates have dropped off a cliff, or a contact mentions they never got your email. Before you blame your subject line, it's worth checking whether your domain or IP has landed on a blocklist. It happens more than people expect, and it can happen to senders who are doing most things right.

Here's how to actually check, not just a list of tools but what to do with them.

Step 1: Know what you're checking

You don't just have one thing to check. You have a few:

• Your sending IP address (or IPs, if you're on a shared pool)
• Your sending domain (the domain in your From address)
• Any link or tracking domains embedded in your emails

IP blocklists and domain blocklists are separate systems. You can be clean on one and flagged on the other, so check both.

Step 2: Run a multi-list scan

The fastest starting point is a tool that checks across multiple blocklists at once. Our free Blocklist Checker is a good place to start. MXToolbox also runs your IP or domain against 100+ lists in one shot and shows you exactly which ones have you flagged.

Run your sending IP first, then your domain. If you use a separate tracking or link domain, check that too.

Step 3: Check the major lists directly

Multi-scanners are great for coverage, but the lists that actually affect delivery are worth checking directly:

• Spamhaus (spamhaus.org/lookup). The most influential blocklist in email. A Spamhaus listing will affect delivery across virtually every major mailbox provider.
• Barracuda (barracudacentral.org). Widely used by corporate email gateways.
• Spamcop. Complaint-driven list, worth checking if your complaint rates have spiked.
• SURBL (surbl.org). Focuses on domains found inside email bodies, particularly link domains.

Step 4: Understand what a listing actually tells you

Finding a listing isn't the end of the world. It's a signal about what went wrong. Most blocklists will tell you the reason for the listing, whether it's spam complaints, a spam trap hit, or suspicious sending patterns. That reason matters a lot because it tells you what to fix before you request removal. Jumping straight to a removal request without fixing the root cause usually results in getting relisted quickly.

But if a listing is on a list you've never heard of, that's not always a crisis. Some blocklists have almost no real-world impact on delivery. Severity varies enormously between lists.

How often should you check?

Once a week is a reasonable minimum if you're sending regularly. Check immediately if you see a sudden drop in open rates, an increase in bounces, or get a report that your emails aren't arriving. Catching a listing early means less damage to your sender reputation overall.

So you can also set up automated monitoring through tools like HetrixTools, which will alert you the moment your IP or domain shows up on a list. That's worth doing if you're sending at any real volume.

Once you know you're listed, the next step is figuring out why before you do anything else. If you're already there and feeling stuck, our SOS hotline is free and we'll help you work through it.