How to Check if Your Domain or IP Is on an Email Blacklist
If your mail suddenly stops landing, a blacklist is a prime suspect. Here is how DNSBLs work, which ones matter, how to check your domain and IP, and how to get delisted.
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If your delivery rate fell off a cliff overnight and nothing about your setup changed, a blacklist is one of the first things to rule out. A single major listing can route your mail straight to spam at thousands of receiving servers at once.
What a blacklist is
A DNSBL (DNS-based blocklist) is a published list of domains and IP addresses associated with spam or abuse. Receiving mail servers query these lists in real time: when a message arrives, the server can check the sending IP against a DNSBL and reject or downgrade the mail if it is listed. Spamhaus, SpamCop, Barracuda, and dozens of others run lists like this.
You can land on one for reasons that are not your fault: a shared IP where a neighbor sent spam, a compromised account that blasted mail before you noticed, or a spam trap address that slipped onto your list and got hit.
Domain vs IP
There are two things that can be listed, and they fail differently:
- Your sending IP is the most common listing and the most immediately damaging, because receivers check it on every message.
- Your domain can be listed too, often based on URLs in the message body rather than the sender.
Checking both matters. A clean IP with a listed domain still has a problem.
How to get delisted
- Find the cause first. Delisting without fixing the source just gets you relisted. Look for a compromised account, a bad sending practice, or spam-trap hits from an unverified list.
- Use the list's own removal process. Most reputable DNSBLs have a self-service delisting form. Submit it once the cause is fixed.
- Give it time. Some lists expire listings automatically once the behavior stops.
The cheapest way to stay off blacklists is to not mail dead addresses and spam traps in the first place. Verifying a list before you send removes the undeliverable addresses and the trap-shaped ones that get you listed.
How to check it
The free blacklist monitor checks a domain or IP against 25 and more DNSBLs and shows you which lists, if any, have it flagged. It does not save the domain or IP you check.
A blacklist is one of five deliverability signals. To see it alongside MX, SPF, DKIM, and DMARC, run the deliverability scan. To stop the problem at the source, read how to reduce your email bounce rate.
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Both Free and Pro run the same scan engine — full SMTP probe, MX lookup, typo, disposable, domain checks, and the evidence chain on every verdict. The difference is the monthly credit pool (Free=500, Pro=100,000) plus Pro's API and MCP access.