How have your last few email campaigns gone? Maybe you’ve noticed a distinct drop in delivered emails, or maybe you’ve received a message delivery failure notification like the following:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one of more of its recipients. This is a permanent error. The following address(es) failed:

[email protected]:
SMTP error from remote server for RCPT TO command, host: (999.99.99.999) reason: 550 Sender IP (99.999.9.999) is blacklisted at

Have you received a bounce message like this? (Pay close attention to the type of error. Does it include the words “Sender IP” and your email address?) Then you might be asking yourself, “Is my IP address blacklisted?” Meaning the answer is yes. But don’t panic. There are steps you can take to remove your IP from the blacklist and avoid being blacklisted in the future.

What is an IP Blacklist?

First, let’s talk about what an IP blacklist is. Cybersecurity companies compile databases of IP addresses that send spam. They share these databases with email service providers to protect users from unwanted email. How does an IP get blacklisted? Here are just a few of the ways these companies figure out who makes it to their list of blacklisted IP addresses:

  • Unusual send volumes – A sudden, large increase in outgoing email is a red flag. Internet service providers (ISP) work with cybersecurity companies to flag IP addresses that are guilty of this abnormal activity.
  • User reports – Recipients of unwanted email can report spam within their email applications and on spam database websites.
  • Spam traps – These are unpublished email addresses you would only find through website scraping or bulk email harvesting. There are also specific email addresses set up to test a company’s unsubscribe process. If you don’t honor an unsubscribe request within a specific time, your IP address gets added to the list.

Email service providers such as Gmail and Microsoft use these IP address blacklists to decide what to deliver to an inbox, what to send to a spam or junk folder, and what to completely block.

Some IP blacklists are more important than others. Here are the most popular and credible blacklists that will affect your deliverability.

How to Check if Your IP Address is Blacklisted

To check if your IP address is blacklisted, the first thing you need is your email server’s IP address. This is different from your public IP address. The easiest way to find your mail exchange (MX) server IP address is by using MxToolbox, where you can look up your address with just your website’s domain name. This will scan your website for your email server and give you an 8-11 digit address. If you have more than one email server, you might see something like this:

Email server ip address lookup results from MxToolbox

Once you have your IP address, you can enter it into the IP blacklist websites. These will check your IP address against several blacklist databases.

A few sites you can use to check if you’re on any blacklists:

Why is My IP Address Blacklisted?

Even if you’ve never sent a single unsolicited email from your IP address, there are several things that could explain how your IP got blacklisted.

  • You’re not maintaining your mailing list properly. If you’re not scrubbing your contact lists frequently, you may have a lot of incorrect email addresses or you may be behind on honoring unsubscribe requests.
  • Someone hacked your email account. Hackers use viruses to get into your email account and take over. You may only find out after it’s too late, potentially from bounce notifications for emails you don’t remember sending.
  • You’ve purchased a bad email list. While it may be tempting to buy email addresses from a third party, these lists can contain spam trap email addresses. Even one of these bad addresses could land you on a blacklist and torch your email marketing efforts.
  • Too many people marked your emails as spam. Many people find it easier to just mark an email as spam than to go through an unsubscribe process. Engaging and relevant emails should minimize this issue.

How to Remove an IP Address from a Blacklist

Once you’ve checked for any viruses and compromised email addresses, you can now actively remove your IP address from blacklists.

Your IP blacklist report should include the blacklist databases your business appears on. Visit each of the blacklisted websites and request removal. Each blacklist will have their own process for removal.

Here’s what the process looks like for the top 6 IP address blacklists.

  • Spamhaus operates several blocklists. Enter your IP address in the Blocklist Removal Center to find out which list you’re on and the instructions for removal.
  • Barracuda requires your IP address, email address, phone number and reason for removal. They typically investigate and process requests for removal within 12 hours of submission — as long as you offer a valid explanation.
  • Spamcop operates a bit differently. It automatically handles blocking and unblocking, so as long as it continues to receive reports of spam from your networks, your IP address will be on the blacklist. The good news is removal happens automatically after 24 hours with no new spam reports.
  • Invaluement adds you to their blacklist if you’re part of a range of IP addresses or domains they classify as spammers. You need to show you haven’t sent spam from your IP address, or prove that you’re on the blacklist because someone else hacked your account.
  • Lashback bases its blacklist solely on whether your IP address attempted to email one of their spam trap email addresses. You get one free slip-up every 30 days, but you’ll have to pay for repeat offenses.
  • PSBL uses spam traps for its blacklist entries. It’s a passive system, so it’s easy to request removal. Even if you don’t request removal, your IP address automatically expires from the list after a few weeks. That is, unless they catch you in another spam trap.

If you’ve ended up on an email blacklist, it’s not the end of the world. Do what you can to fix your security issues, scrub your contact lists, and remove your IP address from those blacklists. If you’re still having trouble, learn why your emails aren’t getting opened, and how to fix it.