How do I find out if my IP or domain is on a blocklist?
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You send a campaign, open rates crater, and someone on your team asks the dreaded question: are we on a blocklist? Here's how to find out fast.
Start with an aggregator. These tools check your IP or domain against dozens of public blocklists in one shot. MXToolbox is the most widely used free option. Enter your IP or domain and it returns a color-coded report showing which lists you're on and which you're clear of. MultiRBL queries even more lists and is worth running as a second opinion.
Check the big lists directly. Some blocklists are weighted heavily enough that you want to confirm your status straight from the source. Spamhaus has a lookup at check.spamhaus.org. Barracuda has one at barracudacentral.org. SpamCop offers a check on their site too. Direct lookups matter because a listing on Spamhaus SBL, for example, affects delivery far more than a listing on a tiny blocklist most mail servers ignore.
Check your sending IPs AND your domain. This is the step most people skip. Some blocklists track IP reputation separately from domain reputation, and URI blocklists check the links inside your messages. If you only check your IP and miss a flagged domain, you'll be chasing the wrong problem.
How to read the results. A listing entry usually tells you which list flagged you, when it happened, and a reason code. That reason code is your first clue toward understanding why it happened. Don't panic if you see a listing on a small, obscure list. Focus first on Spamhaus, Barracuda, and any list that your ESP or ISP specifically monitors.
How often should you check? If you're a high-volume sender, weekly at minimum. If you're seeing delivery problems right now, check today. You don't want to find out you've been listed for three weeks after your open rates already tanked.
The fastest way to get alerted automatically is our free Blocklist Checker. Run it on both your sending domain and your IP, and you'll have a clear picture in under a minute. If you find something and aren't sure what to do next, our SOS hotline is free and we actually help (no sales pitch, promise).
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