How To Remove IP From Barracuda Blocklist? A Comprehensive Guide

5 min read
20 December 2021
Gustavas Davidavičius

The Barracuda blocklist serves an important role, but how does it block IP addresses? And what steps must be taken to remove IPs from BRBL?

How to remove IPs from the Barracuda blocklist.

A brief look inside the average email spam folder will show you just how hard spam filters are working to keep junk mail out of your inbox. One key resource in the email provider’s anti-spam toolbox is the Barracuda reputation system. It blocks emails from blocklisted IPs, which creates a problem for the sender: how to remove IPs from the Barracuda blocklist.

The Barracuda Reputation Block List (BRBL) is a list of IP addresses (single IP addresses or ranges) and domain names that have a link to junk emails. Email delivery services are able to use this list to identify IP addresses that are likely sending inauthentic mail. 

Unfortunately, often through no fault of their own, email servers that are sending legitimate mail sometimes end up on the Barracuda blocklist. Fortunately, Barracuda is aware of this issue and enables the removal of a server’s IP address from their list if you have a valid reason. 

Before we explain how to remove an IP from the Barracuda Reputation Block List, let’s first explore what Barracuda is and how it stops IP addresses from sending spam. 

What is the Barracuda blocklist?

Since 2008, the Barracuda Network has compiled and maintained a list of IP addresses that have sent spam messages. 

This kind of list is known as the Domain Name System blocklist (DNSBL), which is a real-time database containing information about IP addresses and domains suspected of sending spam emails. Mail servers use DNSBL lists to perform Domain Name System queries and to ensure their clients don’t receive spam. 

Flow chart of how DNSBL enables mail servers to check email sender reputation.
DNSBL enables mail servers to check the email sender’s reputation

The Barracuda blocklist is free to use and can help companies fight the spread of junk mail. Barracuda aims to offer its service to everyone other than competitors and, of course, spammers themselves. 

Why can server IPs be blocked?

There are a couple of steps that can help determine whether a sent email is spam or legitimate mail and whether the sender’s IP address should end up on the Barracuda blocklist. 

The first layer of the Barracuda reputation system automatically blocklists an IP address if the connecting machine uses one of the following:

  • Open relays or proxies
  • Spam bot networks
  • Spam trap addresses

Open relays or proxies are tools that allow the sender of an email to hide their identity. If a sender is using either an open proxy or open relay, the IP address is blocklisted. 

Spam bots are computer programs that automate the process of sending spam. If the sending IP address is part of a known spam bot network, the email is automatically flagged as spam. 

Spam traps are email addresses that are leaked to spammers and not used for legitimate mail. If a sender is sending emails to these addresses, they are automatically identified as junk. 

Email over a trap symbolizing a spam trap.
Spam trap

If mail passes through this layer of checks, the Barracuda central reputation system runs additional tests. Using data from its broad anti-spam network, Barracuda generates a score for how likely mail is to be unsolicited. If sent mail falls below the set score, the sender’s IP address is immediately added to the Barracuda blocklist. 

If you suffer from email bounce (mail is being filtered), your server may have ended up on the Barracuda Reputation Block List. Unless you’ve been running a spam bot network of your own, it is possible you’ve suffered a security breach. This might include breaches from user accounts on your server, insecure contact forms on your domains or compromised web applications. 

So, how can you check if your domain is on the Barracuda blocklist, and what can you do if it is? 

Delisting IP addresses from Barracuda blocklist

If you suspect that your IP has been blocked by Barracuda, there are three simple steps you should take to check if you need to request your IP’s removal. 

Note: The steps are relevant for both a server or email administrator and an internet service provider (ISP). If your IP was provided by an ISP or any other organization, that organization should be contacted to investigate the issue further.

1. Check if IP is blocklisted

The first thing you must do if you suspect that your mail is detected by spam filters is check whether your IP address has been added to the Barracuda Reputation Block List.

Access the Barracuda Reputation Lookup tool and perform an IP reputation check against the blocklist. Simply enter your IP address or domain name and click Check Reputation. If you find that your IP has been blocklisted, move to the next step. 

Screenshot of the Barracuda reputation lookup tool page.
Barracuda IP Reputation Lookup

2. Address the blocklist issue

If your server IP exists in the blocklist, you must find the reason why your IP is blocklisted. In most cases, if mail sent from your server was flagged by the blocklist, you should receive a bounceback notification identifying the cause of blocklisting. 

These issues include, but are not limited to:

  • 420 – Your email was deferred due to suspicious content 
  • 451 – Aborted due to a server error
  • 500 – Command not recognized
  • 503 – Bad sequence of commands
  • 535 – Authentication failure

Once you address the issue regarding why your IP has been automatically added to a blocklist, you can move to the final step. 

3. Request removal from the blocklist

If you have addressed the underlying issue that caused the blocklisting of your server, you can send a removal request to Barracuda. 

Access the Barracuda Central Reputation System – Removal Request form and enter your details. The removal form requests your email server address, email address and phone number. Make sure you provide valid information if you want your request to be processed. 

You must also provide a valid explanation for why your server IP should be taken off the blocklist. Make sure you submit your request correctly the first time, since the network ignores multiple requests. 

Once you enter all the details, click Submit Request.

Screenshot of the Barracuda IP removal request form page.
Barracuda Removal Request form


To recap, even if you’re running a legitimate business and sending mail to a valid email address list, you may find that your server is affected by the Barracuda blocklist. 

This is likely because of compromised user accounts and web applications or insecure contact forms on your domain. In that case, Barracuda may determine that your server has been used to send spam emails. 

Luckily, you can fix this in 3 simple steps. First, use the Barracuda blocklist check tools to see whether your server has, in fact, been blocklisted. If your address is on the blocklist, you should then work to identify and fix the issue. 

Finally, use the Barracuda blocklist removal form to submit a removal request and have your server taken off the blocklist. 

After this, spam filters should no longer be triggered by your mail. 

About the author

Gustavas Davidavičius

Senior Abuse Prevention Specialist

Gustavas is a Senior Abuse Prevention Specialist at IPXO. He specializes in the abuse desk policies, as well as IP reputation upkeep on the IPXO’s IP leasing and monetization platform.
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