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You send out emails as usual, but suddenly, some start bouncing back. Others aren't reaching the inbox, and you're not sure what's gone wrong.
One possible reason is that your sending IP address has been blacklisted.
But before you try to remove it, you need to know which blacklist flagged your IP and whether that listing is actually affecting email delivery.
In this guide, I'll walk you through how to check if your IP is blacklisted, find out why it happened, remove the listing, and prevent it from happening again.
Checking an IP blacklist starts with one thing that is easy to get wrong, you need the IP address that actually sends your emails.
Once you have that, you can check it against public blocklists and see whether any listing is connected to your delivery problems.
If you send through an SMTP server, the sending IP is the public IP used by that server to deliver your emails. You may be able to find it in:
Don't assume the IP shown when you search “what is my IP” is your sending IP. That usually shows the public IP of your current internet connection, which may be different from the server sending your emails.
Once you have the sending IP, enter it into an IP blacklist checker such as MXToolbox. The checker will compare the IP against multiple public blocklists and show where it is currently listed.
You can also check the IP directly with Spamhaus to see whether it appears on one of its lists.
If your IP comes back as listed, check where it was listed before taking any action. A listing on Spamhaus or Barracuda may deserve closer attention, while another blocklist may not be used by the mail providers receiving your emails.
Open the blacklist's own lookup page and search your IP there. Look for the type of listing, the reason provided, and any instructions from the blacklist operator. This matters because seeing your IP on a blacklist tells you that it has been listed, but it doesn't tell you whether that particular listing is causing your current email delivery problem.
Next, check whether the listing is actually affecting your emails. Look at recent SMTP rejection or bounce messages. A rejection may mention the blocked IP, name the blocklist being used, or include a link explaining why the receiving server rejected the email.
For example, if your IP appears on several public blocklists but your rejection message specifically points to one of them, you know which listing to investigate first.
Your IP can appear on a public blocklist without that particular list being the reason your emails are failing. Once you know where your IP is listed and whether the listing is affecting delivery, you can investigate why it happened before requesting removal.
There are several free tools you can use to check whether your sending IP appears on a public blacklist. Some check many blocklists at once, while others are useful when you need more information about a specific listing.
MXToolbox checks a mail server IP against more than 100 DNS-based email blocklists. The results show which lists report your IP as listed.
It also has separate tools for checking SMTP, MX records, SPF, DKIM, DMARC, and other parts of your email setup.
Spamhaus has its own IP and Domain Reputation Checker for checking whether an IP appears on one of its blocklists.
If another blacklist checker reports a Spamhaus listing, check the IP directly with Spamhaus. Its lookup can show the listing affecting the IP and direct you to information about resolving it.
MultiRBL is a free tool that checks an IP against multiple DNS-based blocklists. It also performs forward-confirmed reverse DNS checks.
One useful detail is that MultiRBL marks some results as informational. So a result shown by the tool does not always mean your IP is being blocked.
DNSChecker checks IP addresses against multiple DNSBLs, RBLs, and other reputation databases. Its IP tools cover more than 50 anti-spam databases. You can also use its other DNS tools to check records related to your sending setup.
WhatIsMyIPAddress checks an IP against 50 DNS-based anti-spam databases. It gives you a simple way to see which third-party lists report your IP. WhatIsMyIPAddress does not maintain those blacklists itself, so any listing should be investigated with the blacklist provider directly.
A blacklist checker tells you where your IP is listed, not how much that listing is hurting your email delivery. If you find a listing, check the blacklist provider's own lookup and your recent bounce messages before deciding what to fix.
An IP address can get blacklisted when a blocklist detects spam, compromised systems, or other suspicious activity coming from it. The exact reason depends on the blacklist.
Some common reasons include:
Before requesting removal, find out why your IP was listed. The fix for a compromised server will be different from the fix for a spam-related or policy-based listing.
Once you know which blacklist has listed your IP, don't go straight to the removal form. First find out why the IP was listed and fix that problem. Otherwise, the IP may remain listed or end up back on the list.
Start with the blacklist provider's own lookup tool. Search your sending IP and read the information attached to the listing.
For example, Spamhaus tells users to check the listing details to understand the problem before trying to resolve it. The action you need to take will depend on whether you're dealing with spam activity, a compromised system, or a policy-based listing.
Also check your SMTP logs and recent bounce messages. They can help you match the listing with what was happening on your server when the delivery problem started.
The fix depends on the reason your IP was listed. If a server or account was compromised, secure it and stop the unauthorized sending. If the listing is related to spam activity, stop the activity responsible for it and review your sending setup before continuing.
A Spamhaus PBL listing needs a different approach. PBL covers IP space that should not normally send email directly to destination mail servers. If you're legitimately running an outbound mail server on a static IP, Spamhaus has specific requirements for requesting an exclusion, including appropriate forward and reverse DNS. You should fix the issue first. Then move on to removal.
There isn't one removal form that works for every blacklist. For a Spamhaus SBL listing, an end user cannot request removal directly. Spamhaus says the ISP or network responsible for the listed IP must resolve the issue and request removal.
For an eligible Spamhaus PBL listing, a mail server administrator can look up the IP, open the listing details, and follow the removal steps provided there. Barracuda has its own IP reputation removal form. It asks for the mail server IP and contact information, along with an optional reason for the request. Always use the instructions provided for the exact blacklist and listing type you're dealing with.
Once the removal has been processed, search the IP again on the blacklist provider's website. You can then run another multi-blacklist check to see whether the same IP appears on any other lists.
A removed listing may not disappear from every receiving network immediately. Spamhaus says some networks can take longer to receive the updated status.
Removal from a blacklist tells you that the listing has been cleared. It doesn't automatically mean every delivery problem has disappeared.
Check your SMTP responses and bounce messages after you start sending again. If messages are still being rejected, look at the new rejection reason rather than assuming the old blacklist is still responsible.
If the same IP gets listed again, investigate the cause again. Repeatedly requesting removal without fixing the activity behind the listing won't solve the underlying problem.
There is no fixed time for getting an IP removed from a blacklist. Some listings expire automatically, while others require you or your provider to fix the problem and request removal. Here are a few examples:
If your IP is listed elsewhere, check that provider's removal policy instead of assuming the same timeline applies.
Once your IP is removed, the next step is to reduce the signals that can put it back on a blocklist. Focus on list quality, sending behavior, DNS, and server security.
These steps do not guarantee that an IP will never be listed, but they address the common technical and sending issues that can lead to repeat problems.
Infraforge is a private email infrastructure platform for cold outreach. It uses dedicated servers, so you control the sending activity behind your IP instead of sharing the same IP pool with unrelated senders.
That is useful when you are checking or managing IP reputation. With Infraforge, you can:
Infraforge won't prevent an IP from being blacklisted if the sending activity behind it causes a problem. What it gives you is direct control over the IPs used by your cold email infrastructure.
If you want to manage your own private sending infrastructure instead of relying on shared IPs, you can get started with Infraforge.
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Seeing your IP on a blacklist does not automatically mean you need a new IP. In many cases, the better move is to identify the listing, fix what caused it, and follow the blacklist's removal process.
If you send cold emails, it also helps to know exactly which IPs your domains are using and have control over them.
Infraforge gives you private email infrastructure with dedicated IPs. You can check the IP linked to your domain, add more IPs when needed, and manage multiple IPs from the same platform.
So, if you want more control over the IPs behind your cold outreach, get started with Infraforge.