Blacklist monitoring
Nobody emails you to say you have been blocklisted
A Spamhaus listing can stop your mail at the door, and the first sign is usually a customer saying they never got it. We check your sending domains and mail server IPs on a schedule and tell you the hour it happens.
The lists
What a ZEN, DBL or ZRD listing means
Three lists, two subjects. ZEN answers questions about IP addresses; DBL and ZRD answer questions about domains.
Spamhaus ZEN
IP addressesThe combined IP blocklist: SBL for direct spam sources, CSS for snowshoe and low-reputation sending, XBL for exploited machines and open proxies, and PBL for address space that should be relaying through a provider rather than sending directly. Most receivers query ZEN and get all four answers in one lookup.
Spamhaus DBL
DomainsThe domain blocklist. A domain lands here when it appears in spam — as the sending domain, or as a link in the body — or when a legitimate domain is being abused, such as a hacked site or a redirector spammers have borrowed. DBL follows the domain, so changing IP does not help.
Spamhaus ZRD
DomainsZero Reputation Domains: domains registered very recently. It is not an accusation of anything, it is caution about the unknown — but a brand-new sending domain can still be filtered because of it. Most ZRD listings age out on their own.
Want to know where you stand right now? The free blacklist check runs all three lookups and explains the return code — no account needed.
Why it matters
A listing costs you delivery before anything else is considered
Content, subject line and sending history all come after the blocklist lookup. This is the cheapest failure to catch and the most expensive one to miss.
Receivers check before they look at anything else
A blocklist lookup happens during the SMTP conversation, before content filtering, before your reputation, before the subject line. A listing can mean an outright rejection rather than a spam folder.
It is silent from your side
Your sending tool reports the message as sent. The bounce, if there is one, lands in an address nobody reads. Most people find out when a customer says they never received the invoice.
It usually starts small
A single compromised mailbox, an old purchased list, or a shared IP where somebody else misbehaved. Caught in the first hours it is an afternoon of work; caught in the third week it is a rebuilt reputation.
Listings come back
Delisting fixes today. If the cause is still there — the hacked form, the credentials in the wild — the listing returns, which is exactly the case where one-off checks let you down.
How monitoring works
Hourly checks and an alert you will actually receive
The lookups are the same ones a receiver runs. The difference is that they happen on a schedule and the answer reaches a human.
- Step 1
Add what you send from
Your sending domains and the IP addresses of your mail servers. Domains are checked against DBL and ZRD, IPs against ZEN.
- Step 2
We check on a schedule
Hourly checks on paid plans, through the Spamhaus Data Query Service. Every result is stored, so you get a history rather than a snapshot.
- Step 3
You hear about changes
A new listing, or a listing clearing, raises an event and sends an email alert. Pro adds webhook and Slack alerts and a weekly digest.
Getting delisted
How to get a listing removed
Removal requests are granted once the cause is gone. Fix first, then ask.
- 1
Read the return code
Every listing comes back as a 127.x.x.x code, and the code is the reason. SBL, CSS, XBL, PBL and the DBL codes all mean different things and need different fixes. We show the code and what it means.
- 2
Remove the cause
Rotate the credentials on the compromised mailbox, stop the campaign, drop the purchased list, patch the site. Spamhaus re-tests, so a cosmetic fix fails and a failed request makes the next one harder.
- 3
Request removal
Look the IP or domain up in the Spamhaus Blocklist Removal Center, read the evidence they publish, and submit the request from there. Removal is handled by Spamhaus, not by us.
- 4
Watch it stay clean
Keep the monitor running. If the listing returns you will know within the hour, which is the difference between a blip and a lost quarter.
Removal is handled by Spamhaus, not by PilotVerify.
FAQ
Questions about blacklist monitoring
Which blocklists do you check?
The Spamhaus lists: ZEN for IP addresses, which combines SBL, CSS, XBL and PBL, plus DBL and ZRD for domains. Spamhaus is the blocklist most mailbox providers consult first, which is why we cover it properly rather than covering fifty lists shallowly. We do not currently check other operators' lists.
How often are my domains and IPs checked?
Hourly checks are part of the Starter plan and above; the free plan keeps seven days of history, which is enough to catch a listing but not to watch a pattern. While the beta runs, the scheduled check is hourly for every monitor. You can also run an on-demand lookup at any time with the free blacklist check tool, no account needed.
Does being listed always mean my mail is blocked?
No, and it is worth being precise: a listing is a signal receivers choose how to use. Some reject outright on a ZEN hit, some weight it alongside other signals, some ignore certain sublists. A ZRD listing on a new domain is usually just caution. What is consistently true is that a listing makes delivery worse, and that nobody tells you about it.
Can you get me delisted?
No. Delisting is between you and Spamhaus, through their Blocklist Removal Center, and no third party can do it for you — treat anyone who claims otherwise with suspicion. What we do is tell you the moment it happens, show you the return code so you know which cause to fix, and confirm when the listing clears.
I am on a shared IP with my email provider. Is this still useful?
Yes, with a caveat. You cannot fix a shared IP yourself — that is your provider's job — but knowing the IP is listed explains a sudden delivery drop you would otherwise blame on your content, and it gives you something concrete to take to support. Your domain listings, on DBL and ZRD, are yours regardless of which IP you send from.
How many monitors do I get?
Three on the free plan, ten on Starter, fifty on Pro and 250 on Agency. A monitor is one domain or one IP address. Paid deliverability plans are in beta and free to use while the beta runs.
Start watching
Three monitors, free, for as long as you want them
Add your sending domain and your mail server IP and you will know about the next listing within the hour. Paid plans add more monitors, hourly checks and longer history, and are free while the beta runs.