How blacklist checking works
Each blacklist publishes its data over DNS. To test an IP, the address is reversed and looked up inside the list's zone — if it answers, the address is listed, and the accompanying TXT record usually explains why. Domain lists such as Spamhaus DBL and SURBL work the same way but on the name itself, catching domains advertised inside spam messages.
Frequently asked questions
- Which blacklists matter most?
- Spamhaus ZEN, Barracuda and SpamCop cause the most rejected mail. A listing on a small niche list rarely affects delivery.
- Should I check my domain or my IP?
- Both — enter your domain and this tool tests its website IP, its mail server IPs and domain reputation lists in one go.
- How long do listings last?
- Anywhere from a few hours to several weeks. Automatic lists expire once the abuse stops; manual lists need a delisting request.
- I use Google or Microsoft to send mail.
- Their shared IPs are almost never listed, so focus on your domain reputation and your SPF, DKIM and DMARC setup.
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