How Do I Check if My Domain Is Blacklisted – and Get Removed?

A blacklist (blocklist or RBL) is a public list of domains and IPs flagged for sending spam. Mailbox providers check these lists and filter or reject listed senders. Your domain and your sending IP can be listed independently, so always check both.

Start with a multi-blacklist lookup tool like MXToolbox or MultiRBL: enter your sending domain, then your IP, and it queries dozens of lists at once. Follow that with a direct Spamhaus lookup, since Spamhaus is the list that matters most and you want to know its verdict specifically. Then read which list actually flagged you, because they don't carry equal weight. To confirm a listing is really the thing hurting you, run a seed test across Gmail, Outlook, and Yahoo and check Google Postmaster Tools. A major-list listing plus spam placement and a red reputation is your confirmation; an obscure list with clean placement usually isn't worth chasing.

Here's how the lists that come up most often stack up:

Removal is pointless until you fix what triggered the listing, so start there. By far the most common cause is a bad list: scraped or stale data drives bounces, and a single spam trap hiding inside it – an address that exists only to catch senders using bad lists – can land you on Spamhaus instantly.

Close behind are spam complaints, where enough recipients marking you as spam pushes you onto complaint-driven lists. The rest are variations on looking suspicious: a sudden volume spike from a new or cold domain reads like a compromised sender, missing SPF, DKIM, or DMARC makes you look like a spoofer, and on shared infrastructure someone else's behavior can get the IP listed before you've sent anything at all.

Be realistic about which domain you're fighting for. Your main domain is always worth saving: fix the cause, delist, and then never send cold mail from it again – keep outreach on separate domains so this can't reach your real email. A dedicated cold-outreach domain is a different calculation. If it's listed on Spamhaus and tied only to outbound, retiring it and spinning up fresh, properly warmed domains is usually faster and cheaper than nursing reputation back, because domain reputation is sticky and the ceiling stays low even after removal.

Blacklisting is downstream of bad sending practice and bad infrastructure, so the durable fixes are structural. The single highest-leverage habit is verifying every list before it touches a live mailbox – cheap data that bounces is the most expensive data there is, and it's the fastest path onto a blocklist. From there it's the same discipline that keeps you out of spam generally: send cold mail only from dedicated domains so a listing never reaches your main one, authenticate every sending domain with SPF, DKIM, and DMARC, warm new mailboxes while keeping per-mailbox volume low and spread across many of them, and run a weekly blacklist check plus seed tests so you catch a listing before it tanks a campaign.

Maildoso provisions domains and mailboxes with authentication auto-configured and warmup built in, on infrastructure managed for sending reputation – so the bounces, spikes, and misconfigurations that get domains blacklisted are handled before they start.