How to Check if Your Sending Domain Is Blacklisted, and Fix It

Look for these signs before you run any checks:

• Bounces that mention blocking. Rejection messages with wording such as "blocked," "listed" or "denied due to reputation," often include a code and a link explaining why.
• A sudden increase in bounces from one provider or across several.
• Replies drying up while your sending volume stays the same.
• Test messages landing in spam at several providers at once.
• Complaints from your team that colleagues can't reach recipients they normally can.

Any one of these can have other explanations, such as an authentication failure or a bad list, so confirm before you act.

Work through them in order:

1. Collect the details. Note the sending domain, the IP address the mail is sent from (find it in a message's headers) and the date the problems began.
2. Read a bounce message in full. The response text is the first place to look. It may name a blocklist or a policy rule.
3. Run the domain and the IP through several blocklist lookup tools. Use more than one, because no single checker covers every list. Note which lists show you and how serious each is.
4. Verify authentication. Confirm SPF, DKIM and DMARC pass for the domain. Missing or failing records can produce the same symptoms as a listing.
5. Test inbox placement by sending to seed addresses at major providers. A mailbox monitoring tool such as MailReach can scan domains against many lists and track placement over time, which saves manual checking.

If you use a shared IP from a sending platform, the IP's listing may not be your fault, and the platform's support team is the right contact.

Removal requests without a fix tend to be refused or reversed. Work out why you were listed:

• Poor list quality: invalid addresses, purchased lists or old contacts cause bounces and spam traps. Clean the list and verify addresses.
• High complaint rates: irrelevant messages or hard-to-find opt-outs drive complaints. Tighten targeting and make unsubscribing easy.
• Compromised accounts: stolen credentials can send spam without you knowing. Reset passwords and enable multi-factor authentication.
• Volume spikes: sending far more than usual from a young domain looks abusive. Cut volume and ramp again.
• Missing authentication: publish and test SPF, DKIM and DMARC.

Pause campaigns from the affected domain while you fix the cause. Continuing to send while listed makes the record worse.

Each blocklist has its own process, and it's usually described on the list's own website. Some delist automatically after a period without bad traffic. Others need you to submit a form with details of the fix. Follow these rules:

1. Read the list's policy so you know what evidence it wants.
2. State plainly what caused the listing and what you changed.
3. Submit the request once. Repeated requests can delay the outcome.
4. Keep sending paused, or at very low volume, until the listing clears.
5. Check the lookup again after the list confirms removal.

If the listing doesn't clear, or your reputation has been damaged with mailbox providers rather than a specific list, a repair service can help. InboxAlly fits that case: it's built to help restore inbox placement for a domain whose reputation has slipped.

Prevention is mostly routine. Verify every list before you send, and remove addresses that bounced in earlier campaigns. Keep each mailbox's daily volume steady and modest, with cold outreach on separate domains from your main company email. Make the unsubscribe path obvious and honor requests quickly, since spam complaints damage your reputation.

Check authentication and placement monthly, not only when something breaks. Add a written rule for your team: any jump in bounces or drop in replies pauses that mailbox the same day until someone looks at the cause. A five-minute pause is cheaper than a week of sending into a filter you can't see.

Then the problem is likely reputation with providers such as Gmail or Microsoft, which use internal filters rather than public lists. Check authentication, review recent campaigns for complaints and content that looks like spam, and reduce volume. Consider moving campaigns to a warmed secondary domain while the affected one recovers, as described in warming up a new domain and setting up secondary domains.

Prevent repeat problems with a monthly review. The cold email deliverability audit checklist gives a routine to follow, and preventing AI SDR domain reputation meltdowns covers automated sending risks.