What to do if your domain is blacklisted

A blacklist, in email terms, is a list of domains and IP addresses that mail providers check against before deciding whether to deliver, filter or reject a message outright. There is no single blacklist — dozens of independent ones exist, run by different organisations, and a domain or server can be listed on some without being listed on others. Being blacklisted does not mean anyone is targeting you personally; it almost always means an automated system flagged a genuine pattern, even if the underlying cause turns out to be something outside your control.

Signs you might be blacklisted

• Mail that used to arrive reliably now consistently lands in spam or is rejected, for one recipient or for many.
• You receive bounce messages mentioning a blacklist by name, or referencing being "blocked" or "listed".
• A specific mail provider — often one of the larger ones — is rejecting your mail while others accept it fine.

Checking whether you are actually listed

A number of free online tools let you check a domain or IP address against dozens of blacklists at once, returning a clear pass or fail for each one. Run both checks — the domain name itself and, if you know it, the IP address of the mail server sending your messages — since a domain and its sending server can be listed independently of each other.

What usually causes a listing

• A compromised mailbox or website form sending spam without the owner's knowledge — often the actual cause when a previously clean domain suddenly appears on a list.
• A high bounce rate, from sending to a list containing many addresses that no longer exist.
• A sudden spike in sending volume, which some blacklist operators treat as a spam-campaign signal on its own.
• Missing SPF, DKIM or DMARC records, making it easier for someone else to send forged mail that appears to come from your domain, which then gets your domain blacklisted for behaviour you did not cause.
• Complaints from recipients who marked genuine mail as spam, which some blacklist operators use directly as a signal.

Getting delisted

1. Find and fix the actual cause first

   Requesting removal before the underlying problem is fixed usually results in being relisted shortly afterwards. Check for a compromised mailbox — a sudden password change with no corresponding action from the account holder is a strong hint — and check your authentication records are correct.

2. Change any compromised passwords

   If a mailbox was sending spam without your knowledge, change its password immediately and check whether any mail client or app on an unfamiliar device is still connected to it. See changing an email account password.

3. Put SPF, DKIM and DMARC in place if they are not already

   This closes off one of the easiest ways for someone else to send spam that gets your domain blamed. See SPF, DKIM and DMARC explained.

4. Submit a delisting request to the blacklist operator

   Each blacklist has its own removal process, usually a form on its own website, and most explain what they expect to see fixed before approving a request. Follow the specific process for each list you appear on — there is no single request that clears every list at once.

5. Wait out the ones with no manual process

   Some blacklists remove entries automatically once the flagged behaviour stops for a period of time, with no request needed at all.

Preventing it happening again

• Keep SPF, DKIM and DMARC published and check DMARC reports periodically for senders you do not recognise.
• Use a strong, unique password on every mailbox, and change it immediately if you suspect compromise.
• Clean mailing lists of addresses that consistently bounce rather than continuing to send to them.
• Keep sending volume reasonably consistent rather than sudden large spikes, where practical.

If your mail is being filtered but a blacklist check comes back clear, the cause is more likely reputation or content-related rather than a listing — see why your emails go to spam for the fuller set of possible causes.