A blacklist, now usually called a blocklist, is a list of domains or IP addresses that have been linked to spam. Many email systems check these lists. If you are on one, your emails may be sent to spam or rejected without anyone seeing them.
Being listed is less common than people fear, especially if you use a reputable email marketing tool. But if your emails suddenly stop arriving, it is worth checking.
Signs you might be listed
- Your emails suddenly bounce with messages mentioning a blocklist, a block or a policy.
- People tell you your emails are missing, across several email providers.
- Your open and click rates drop sharply from one send to the next.
Two things can be listed
- Your domain, like yourbrand.com. This follows you to any email tool you use.
- An IP address, the server address your emails are sent from. If you use a shared email marketing tool, you share IP addresses with other customers. The tool manages these and usually fixes problems quickly.
Most small senders should focus on their domain.
How to check
Use a free blocklist checking tool. Several well known websites let you type in your domain or IP address and check it against many blocklists at once. Search for a "blacklist check" or "blocklist lookup" tool from a reputable email or network company.
To find your sending IP address, open one of your emails in Gmail, choose "Show original" and look in the headers for the sending IP. Or ask your email tool's support team.
Note that some smaller blocklists are rarely used by major inbox providers. Being on one of those usually matters much less than being on a major one. If you are unsure, ask your email tool's support team which listings matter.
Why domains get listed
- Sending to bought, scraped or very old lists.
- Hitting spam traps, addresses created to catch senders with poor list habits.
- Lots of spam complaints.
- A hacked website or email account sending spam without your knowledge.
- Links in your emails pointing to a website that has been flagged.
How to get removed
Step 1: Fix the cause first. Requesting removal without fixing the problem usually means you get listed again quickly. Clean your list, stop sending to old or bought contacts, check your website and email accounts for hacking, and make sure your domain is properly authenticated.
Step 2: Read the listing details. Each blocklist explains why you were listed and how removal works. Some remove listings automatically after a period with no new problems. Others have a request form.
Step 3: Request removal honestly. If there is a form, explain briefly what went wrong and what you changed. Be polite and specific. Blocklist operators deal with many requests and appreciate clear answers.
Step 4: Contact your email tool. If an IP address is listed and you use a shared email tool, tell their support team. They often handle removal for you.
Step 5: Send carefully afterwards. Restart with your most engaged subscribers and grow slowly, much like warming up a new domain.
How to stay off blocklists
- Only email people who opted in.
- Use double opt in to keep out fake and mistyped addresses.
- Remove bounces and inactive contacts regularly.
- Keep spam complaints very low with clear unsubscribe links.
- Authenticate your domain with SPF, DKIM and DMARC.
- Keep your website and email accounts secure with strong passwords and two step login.
The short version
If your emails suddenly vanish, check your domain on a blocklist tool. If you are listed, fix the cause, follow the blocklist's removal process and restart gently. Good list habits keep you off these lists in the first place.
Mailbox providers update their filters and requirements regularly. This guide was last reviewed on January 27, 2026. Spotted something out of date? Tell us.