Crawvix Editorial Team
· Published October 28, 2026 · Last updated October 28, 2026 · 6 min read
An email blocklist (also called a DNS blocklist or DNSBL) is a list of IP addresses or domains that the list's operator associates with spam or abuse. Receiving servers may consult one or more lists and reject or filter mail that matches. Being listed does not always mean you did something wrong: a shared IP address, a hacked mailbox or a vulnerable contact form can all cause it. Removal depends on each list operator, and no one can promise how quickly or whether a listing will clear.
Before you begin
Collect two things: the IP address your mail is sent from (your provider or the full headers of a sent message will show it), and your sending domain. Also find the bounce message for rejected mail. It often names the list, for example in text such as a rejection that mentions a list's domain name. If you send through a shared service such as a mailbox provider or newsletter tool, the IP address belongs to the provider and you will probably need to contact them rather than the list.
Step-by-step instructions
Step 1: Confirm the listing on the list's own website
Use the list operator's own lookup page, not a third-party aggregator, because those can be out of date and may not show the reason. Many lists refuse DNS queries that arrive through large public resolvers or high query volumes, returning a special answer instead of a real result. That is why a plain lookup through a public resolver may say nothing useful, and why Crawvix reports Not checked yet, not Pass, when a list refuses its resolver. Read the reason the list gives. Some lists describe which part of the list you are on and what that means.
What success looks like: You know the exact list, the address or domain listed, and the reason it gives.
Step 2: Work out the cause before asking for removal
Common causes include:
A compromised mailbox or stolen password sending spam.
A website contact form, plugin or script that an attacker is using to send mail.
Malware or an open relay on a server.
A shared IP address where another customer sent spam.
A mailing to a purchased, old or unconfirmed list that generated complaints or spam traps.
A newly assigned IP address with a poor history or no reverse DNS.
For a domain listing, links to your domain appearing in spam, or hacked pages on your site hosting spam or phishing.
Check the mail queue and logs, recent sending volumes, and which accounts and forms sent mail. If the IP is shared, ask the provider.
What success looks like: You can name the most likely cause, or have asked the provider for theirs.
Step 3: Stop the problem and clean up
Change passwords of affected mailboxes and turn on multi-factor sign-in where it is offered. Update or remove vulnerable plugins and scripts, add rate limits and a CAPTCHA to forms, scan for malware, and remove hacked pages. Remove unconfirmed or complaint-prone addresses from lists. Make sure SPF, DKIM and DMARC are set up so abuse of your domain is visible (see the related guides). A removal request made while the cause is still active tends to fail, or the listing returns.
What success looks like: The cause is stopped and you can say what you changed.
Step 4: Request removal through the list's process
Follow the removal process published by the list operator. Some lists remove listings automatically when the abuse stops; others need a request form. Be factual and brief: say what happened and what you fixed. Do not submit repeated requests, and be cautious about third parties that charge for removal. Check the list's published policy. Some listings, for example for address ranges that should not send directly to other servers, are removed through a different process, such as sending through your provider's authenticated mail servers instead.
What success looks like: A removal request is filed or you have confirmed the listing is set to expire on its own.
Step 5: Verify and keep watching
Check the list again on the operator's page, send test mail to the receivers that were rejecting you, and run the Crawvix blocklist check. Keep an eye on bounce messages and DMARC reports for a while to confirm the problem has not returned.
What success looks like: The list no longer shows you, and mail to the previously rejecting receivers is accepted.
Step 6: Enter your sending IP in Crawvix
The Crawvix blocklist check looks up your domain on three domain lists (Spamhaus DBL, SURBL, URIBL). If you enter your sending IP address in the email settings, it also looks it up on three IP lists (Spamhaus ZEN, SpamCop, Passive Spam Block List). Without an address, the check says so and cannot return Pass. Other lists exist that it does not query. A pass means the lists we asked do not list you at that moment. It does not mean your mail will reach inboxes.
What success looks like: The check shows a result for both your domain and your sending IP.
Final verification checklist
You know which list, which address or domain, and the stated reason.
The cause is found and stopped, and passwords and plugins are secured.
You followed the list operator's own removal process.
Test mail is accepted by the receivers that were rejecting it.
SPF, DKIM and DMARC are in place so abuse is easier to spot.
Your sending IP is entered in Crawvix so the IP lists are checked as well.
Common mistakes to avoid
Requesting removal before fixing the cause.
Using an aggregator or a public resolver result as the final word.
Submitting the same request over and over.
Paying a third party that promises removal.
Assuming a clean lookup on one list means no list has you.
Treating a listed shared IP as your own fault without asking the provider who else sends from it.
Troubleshooting
My lookup says listed but my provider says no
Providers often send from many addresses. Find the exact IP in the headers of a message that bounced and look up that one.
The list refused my query
Some lists do not answer queries from public or shared DNS resolvers. Use the list operator's own web lookup instead.
The listing returned after removal
The cause is probably still active. Look again for compromised accounts, vulnerable forms or lists that generate complaints.
I am on a list for addresses that should not send directly
Such lists cover ranges such as home or dynamic connections. The usual fix is to send through your mail provider's authenticated servers instead of from the server itself.
Only one receiver rejects my mail
That receiver may be using its own filtering, not a public list. Read its rejection text and its sender guidelines.
Frequently asked questions
Does a clean blocklist result mean my mail reaches the inbox?
No. Receivers also use authentication results, complaint rates, engagement and content. Blocklists are one signal among many.
How long does removal take?
It depends on the list and on whether the cause is fixed. Do not rely on a fixed time.
Do I need to enter my IP address?
For the IP lists, yes, because we cannot see which server your mail leaves from. The domain lists are checked without it.
Can I check for other lists?
Yes, using each operator's lookup page. Prefer lists that major receivers actually use.
Related guides
Official references
List policies and removal processes change, so a human should check these sources for the current wording before this guide is published.
Next step: See how Crawvix checks a website and capture a baseline once scanning opens. This guide provides technical information, not a guarantee of inbox delivery, rankings or index inclusion.