You sent a campaign this morning and everything looked right. Just about an hour later your inbox has hundreds of bounce messages in it.
Every bounce message has a version of the same line: 550 5.7.1 Service unavailable; client host [198.51.100.20] blocked using Spamhaus, and then a URL.
You paste the URL in, and a page tells you your sending IP is blacklisted.
This is exactly what happens when your email sending pattern break the rules.
There are ways to get off the list but the important thing to address is - why was your domain or ip blacklisted?
First let me give you a quick run down on how to know if your email domain or ip is blacklisted.
How do I know if my email domain is blacklisted?
The easiest way to know this is from the rejection message names the list and almost always links to it. If you are not getting bounces but your open rates fell off a cliff, you are probably not on a public blacklist. You are in a mailbox provider's bad books, which is a different problem.
Being blacklisted by a mailbox provider means there is no lookup page and no form.
The starting point is to look at the non-delivery report.
An SMTP 550 with a phrase like "blocked using", "listed by" or "on the SBL", and a URL. That URL is the authority. Is it your sending IP address, or your domain? And if it is the domain, is it the one in your from-address or the one in your links? Those can be different, and they get listed for different reasons.
Then you need to run an email blacklist check on two things separately: your sending IP, and your domain. The deliverability checker does both against the major blocklists and shows SPF, DKIM, DMARC and MX in the same pass.
Google Postmaster Tools and Microsoft SNDS show you what Gmail and Outlook think of you.
Know what does not count as blacklisted. One campaign in the spam folder. One person hitting "report". A sender score of 84 on its own. Those are reputation signals but they are not a named entry on a named list.
A blacklist is backed by evidence on a specific url.
Should you act on every one of the sixty lists those tools check? No.
A short list that moves inbox placement is Spamhaus, with Barracuda. SpamCop is also good but a step behind. UCEPROTECT and SORBS listings rarely changing anything.
What kind of blacklist am I actually on?
Your domain or ip could be listed one more more blacklists and the fix for each is different.
A public DNS blocklist like Spamhaus has a lookup and a removal form.
A mailbox provider's internal reputation system, like Google's or Microsoft's, has neither.
Your own email platform's suppression list is their decision. You need to find out which one you are dealing with before you do anything else.
Public DNS blocklists.
These are the ones people mean by "an RBL". Spamhaus is the one that matters: the SBL for known bad senders, the CSS for snowshoe spam, the PBL for IPs that should not be sending mail directly at all, the DBL for domains.
Does a DBL entry mean your domain is finished?
No. It means your domain, or a link domain inside your emails, is on a list of blacklisted domains that Spamhaus rebuilds constantly, and it comes off the same way it went on. Barracuda and SpamCop sit a step below, and SpamCop lists fast on complaints and clears itself fast when they stop.
Then there are the ones you can usually ignore. UCEPROTECT lists entire IP ranges to put pressure on hosting providers, and it will happily take a payment to move you up the queue. SORBS is slow and inconsistent.
The mailbox providers' own systems.
Gmail, Outlook and Yahoo do not check a public list to decide about you. They score you themselves, on your domain and IP history, your authentication, your complaint rate and your spam-trap hits. Picture a club with a bouncer who remembers faces. There is no written record to appeal. You stop turning up drunk, you have a run of quiet nights, and eventually he waves you through without thinking about it. Microsoft at least gives you a mitigation form and SNDS. Google gives you Postmaster Tools and a bulk-sender form. This is the list that decides whether your mail lands, and it is the one with no button.
Your email platform's blocklist.
If you send through a shared IP pool, another customer's behaviour can get the shared IP listed, and your platform may suppress your sends or move you to a different pool. If the listed IP is not yours alone, this is the platform's job. Open a support ticket, not a removal request, because you cannot delist an address you do not control.
How do I get my domain removed from a blacklist?
Fix what got you listed first. Then, for a public list, submit the removal request, which is usually a form and a short wait. For an internal reputation system there is no request to submit: you send clean mail to people who want it, for a few weeks, and the score climbs back.
Here is the order, and the order is the point:
| Step | Do this | Why it is here |
|---|---|---|
| 1 | Find the cause. A compromised mailbox, a signup form with no protection, a bought segment, an insecure server on the same IP, an SPF record loose enough for a spoofer to pass. | Every list re-checks on removal. Skip this and the second listing comes faster and stickier than the first. |
| 2 | Fix it and be able to show it is fixed. Rotate the credentials, lock the form, delete the bad segment, tighten SPF, subscribe to the feedback loops. | The removal form for a serious list asks what changed. "Nothing yet" is not an answer it accepts. |
| 3 | For a public list, use the operator's own removal form. Spamhaus re-tests the moment you submit and clears you automatically if the problem is gone. | It is free, it is fast, and it is the only route that sticks. |
| 4 | For an internal system, file the mitigation request where one exists, then send. Small volume, your most engaged people, steady schedule. | There is nothing to remove. There is only a score to rebuild. |
| 5 | Watch. Postmaster Tools and SNDS for the providers, a weekly blocklist check for the public lists. | A listing you catch in a day is an afternoon of work. One you catch in a month is a rebuild. |
What if you genuinely cannot find the cause? Then assume it is the signup form or a leaked SMTP credential, because those are the two that send without ever showing up in your sent folder. Lock both and watch what happens.
How long does it take to get off an email blacklist?
If you are on a public list, it can take anywhere from hours to a couple of days once the cause is fixed. In case of an internal reputation issue with a mailbox provider, it can take anywhere from two to six weeks of consistent good sending. If you skipped the cause, it never really ends, because you keep getting re-listed.
Why weeks and not days? Because the internal score decays and rebuilds slowly, the same way sender reputation always does, and what decides whether your email lands covers that mechanism in full.
A small dip clears in a couple of weeks of normal sending. A domain that has been firing a bought list for months can take two to three months, and there are cases where warming a fresh subdomain properly is faster than rehabilitating the old one.
Why does my domain keep getting blacklisted?
Because the listing was the symptom and you treated it as the disease. You submitted the removal, the mail flowed for a few days, and then whatever was generating the spam-trap hits and the complaints did it again.
Which of these is it, usually? The signup form or the credential leak, nine times in ten, because they are the two that keep sending while you are looking somewhere else. The full list of repeat offenders, in the order I tend to find them:
- A signup form with no captcha or double opt-in, quietly sending a confirmation email to every address a bot types into it, spam traps included.
- A compromised mailbox or a leaked SMTP credential, sending on your domain without a trace in your sent folder.
- A shared server where another site is the real sender and your domain just shares the neighbourhood.
- An SPF record ending in
~allwith an include list you stopped tracking years ago, so a spoofer sends "as you" and passes the check. Tightening that and adding a DMARC policy is a separate job, and SPF, DKIM and DMARC walks through it. - A purchased or scraped segment you paused instead of deleting, and then someone re-enabled.
- Feedback-loop complaints you are not set up to receive, so the people asking to be left alone are invisible to you.
Fix the source and a blacklisting is a once-ever event you barely remember.
Start here
Observe the bounce message. Write down the exact IP or domain it names and the list it points to.
Check both in the deliverability checker, then open Google Postmaster Tools and Microsoft SNDS to see what the two providers that matter most actually think of you.
If it is a public list, find the cause before you go near the removal form, because the form re-checks and a failed request is on record. If there is no list to find and your mail is simply not landing, you are not blacklisted in the form-and-appeal sense. What decides whether your email lands and the order to fix deliverability in are the two pages to work through instead.
And whatever the list, whatever the wait: do not pay anyone to make it go faster.
Related reading
Deliverability
Why Your Emails Go to Spam and What to Do About it?
Your emails are going to spam and every guide points at your subject lines. That is the last thing to fix. Start with your sender score and work down in order.
Deliverability
Email Deliverability: What Decides Whether Your Email Lands
Deliverability is not delivery. Your sending domain carries a score, below 90 is a warning, and the fix is rarely the one people reach for first.
Deliverability
SPF, DKIM and DMARC: What Each One Does and the Order to Set Them Up
Three DNS records answer three different questions about your email. Set them up in the wrong order and you will block your own mail.
Where to go next
Ecommerce
Most stores spend to acquire a customer once and then let them go quiet. The margin is in the second, third and fourth purchase, and that is an email problem rather than an ads problem.
How we work
The services behind this: strategy, lifecycle, deliverability and the testing that decides what actually changed.