How to check if your IP is on an email blacklist
Updated 7/20/2026
Blacklists (or blocklists) are lists of IPs considered spam sources. If your IP ends up on one, your emails are rejected or marked as spam.
1. Check the IP
There are free online services that check dozens of known blacklists at once. You enter the server IP and see which lists it appears on.
2. Check from the terminal
You can query a blacklist manually (generic example):
dig +short 10.113.0.203.zen.spamhaus.orgA reply means the IP (reversed here) is listed. No reply means it is not.
3. What to do if you are listed
- Find the cause: a compromised account, a script sending spam, or an IP with a bad history.
- Fix the problem (change passwords, stop the script).
- Request delisting on the blacklist's website.
4. Prevent
- Configure SPF, DKIM and DMARC correctly.
- Set reverse DNS.
- Filter outgoing spam, see spam filtering.
Put this guide into practice on your own VPS
EU cloud servers, billed hourly, ready in minutes, with one-click installs for dozens of apps.
See pricingRelated tutorials
How to filter spam with Rspamd
Rspamd is a modern, fast spam filter. Here is how to use it to keep your inbox clean.
Updated 7/20/2026EmailHow to secure a mail server
A misconfigured mail server becomes a spam source. Here are the essential security rules.
Updated 7/20/2026EmailHow to use an SMTP relay for reliable delivery
An SMTP relay sends your emails through a service with good reputation, ideal for apps without their own mail server.
Updated 7/20/2026