Email Blacklists: Complete Overview 2023

The Warmup Inbox Team
The Warmup Inbox Team

(Note: Some have started using the term “blocklist” in place of “blacklist” because of negative associations with the word. Both words have the same meaning and can be used interchangeably.)

What Is an Email Blacklist?

Email marketing is one of the most efficient and effective ways to engage with your target audience. The issue with the rise of email marketing is the increase of spam messages that make their way into consumer inboxes. In order to mitigate the plethora of unwanted and malicious content, solutions worked to prevent known spammers and scammers from sending out emails. One of these solutions was the adoption of blacklists.

An email blacklist is an online collection of email addresses and domains that have been identified as sending out spam or malicious content. ISPs use these lists to determine the safety of accepting messages from unknown domains and addresses.

While blocklists are an excellent way to protect consumers, having your business’s email placed on a blocklist can throw a massive wrench in your marketing efforts. Regardless of whether you’ve been sending out malicious content or not, being placed on a blocklist is like having an instant moratorium put on your messages. And when you’re trying to move people through your sales funnel, being unable to deliver your messages can bring your marketing strategy to a full stop.

How Do Email Blacklists Work?

Every email address is attached to a specific IP address that allows ISPs to trace the location of the sender. Your IP address is the electronic version of a return address and will enable ISPs to verify that a message is coming from a reputable sender.

When an ISP gets a message, they first check the sender’s IP address across the DNS blocklists. If the IP address matches one on a blocklist, the ISP rejects the email, but if the IP address doesn’t have a match, the ISP will run a couple more security checks before permitting the message to go through. Blocklists aren’t the only component of email deliverability, but placement on a blocklist has one of the most drastic effects on deliverability rates.

What Does Being Blacklisted Mean?

To put it simply, being placed on a blacklist means that your emails will not reach your desired recipients.

But on a broader scale, being blacklisted can also mean:

  • Your account was hacked, and someone has been sending spam or malicious emails on your behalf
  • You’re sending messages through a shared IP, and someone else on the IP address has been sending out spam or malicious emails (in this case, you may want to consider a dedicated IP)
  • Your IP or domain is brand new, and you have to warm it up first
  • Your IP or domain wasn’t warm enough for you to send out as many emails as you did
  • You’ve had multiple spam reports on your previous messages
  • Your mailing list is filled with old or inactive emails
  • Your sender reputation is bad
  • Your sender score is too low
  • You fell into too many spam traps
  • You haven’t honored unsubscribe requests

No matter the reason you ended up on a blocklist, as long as you aren’t sending out malicious content, it should be relatively easy to get delisted and repair your reputation.

How Can I Tell If I’ve Been Blacklisted?

If you’re attempting to send out emails and nothing is being delivered, you should check to see if you’ve been placed on a blocklist. There are multiple online tools you can use to check if your IP address or domain is on a blocklist:


How It Works

Barracuda Reputation Block List

free DNS blacklist that lists emails known to send spam


anti-spam DNSBL that blocks senders who send out unsolicited mass emails


a way to check multiple blacklists quickly and check your DNS


free multiple DNS service that cross-references lists by IPV4, IPV6, or domain


lists IPs that have been reported as spam by SpamCop users


DNSBLs used to identify and track spam sources


lists websites that have appeared in unsolicited messages

Warmup Inbox

as a part of our platform, we constantly run checks to make sure you’re not on any blocklists

What Should I Do If I’ve Been Blacklisted?

If you are placed on a blacklist, there’s no need to panic and get a brand new IP. Typically, getting delisted is as simple as requesting to be removed by the administrator. Removing your address from a blacklist will vary depending on which list you’re on. As soon as you identify which list you’re on, you can contact the list administrator to figure out the next steps.

Here are some common lists and how to get off of them:


How to Get Delisted


Create a SORBS account and request delisting

Trend Micro

Request delisting


Look up your reputation and request delisting


Look up your reputation and request delisting


Request delisting


Request delisting on all four lists: RATS-Dyna, RATS-noPtr, RATS-Spam, RATS-Auth


Remove hacker or spoofer, create an 0spam account, and request delisting


Request delisting


You’ll automatically be delisted after 24 hours without a spam report


Request delisting


Request delisting


Secure your web server, get your IP address off of all blocklists, set an SPF record, set up a PTR record, verify your mail server setup, and request delisting



Review the Bulk Sender Guidelines and complete the Bulk Sender Contact Form

Different Types of Email Blacklists

There are over 300 public blocklists, and they can be broken down into four categories of lists that affect email deliverability:

New Domain Email Blacklists

Newly registered domains under a domain provider are automatically added to a blocklist for the first couple of weeks after its creation. New Domain lists prevent spammers from creating new domains to send out bulk emails.

Spam Trap Email Blacklists

ISPs use abandoned email addresses as spam traps to detect when people send out emails to random addresses. If someone sends an email to one of these addresses, then the sender is added to a blocklist because attempting contact with an old email address looks suspicious. As long as you constantly update your database and don’t buy old email lists, you should be able to steer clear of these blocklists

Phishing and Ransomware Blacklists

If you’re reported for sending out malicious content, your address will automatically be added to a blocklist. These lists identify known cybercriminals and are the most difficult lists to get off.

Spam Blacklists

If you are on a blocklist, it will likely be a spam list. If you send enough emails and get enough spam reports, you’ll find yourself on a spam list. The good news is that these are the most manageable lists to be removed from and repair your reputation.