Barracuda Blacklist

Published on 2020-04-29· Updated on 2023-09-04


Barracuda Networks is a security service provider that focuses mainly on storage and networking products. The company has an array of several security products that focuses primarily on the web, email, malware, and spam protection.

Barracuda Central, which is a part of Barracuda Networks services, maintains the blacklist and runs the RBL as a service.

Barracuda provides Barracuda Reputation Block List (BRBL). BRBL is a list of domains that can be used for IP lookups to match blacklisted domains in real-time. They are considered as one of the most prominent blacklist providers and, are one of the most reliable when it comes to accuracy, with the fewer number of false positives.


Barracuda Resources

Barracuda uses multiple resources to populate their blacklist; these are discussed in detail below:

Spam traps are a set of email addresses that RBL's like Barracuda creates and maintains. BRBL uses these addresses to trap spammers who mostly try to web scrap as many email addresses they can, to do spam.

It is tough to identify the email traps since they look like a valid email address to which the emails can be sent. Once you submit your emails to these spam traps, you'll get immediately added to the blacklist.  

Getting added to the blacklist could be a result of a hacked email account, or sending emails from an Open Relay SMTP server. You can even get listed for sending mass marketing emails and not following good email sending habits (You don't comply with the can-spam act).

Significant amounts of IP data come from Barracuda Network's large installed base of hardware anti-spam software. The barracuda network has a large set of security products that are installed globally on many devices. The data from all the security products such as anti spams are used to identify and filter domains into blacklists.

You cannot directly add any domain you consider as suspicious to the BRBL list. The additions made to the list are automated and depend upon the algorithms and rules defined by Barracuda services.

Listing criteria

Barracuda has a set of various Open relay servers, spam proxies, and spam traps. Once anyone uses these, they are instantly listed in the BRBL list.

Barracuda has a Barracuda Reputation System (BRS), in which they have a list of domain IPs with their respective reputations according to the Barracuda. 

Even if the IP address is checked in the BRBL and is passed, the emails do start getting scored against The Barracuda Reputation System. And these IP's are listed the instant they are detected having a "poor" reputation in BRS.   

Reasons for your IP address or domain been listed with a poor email reputation score:

  • Your email server is compromised and may be sending spam messages without you knowing.
  • Your email server is misconfigured.
  • Your system is being infected with a virus or botnet software program.
  • You may be using a shared IP address which is/was used by a spammer which is affecting your domain.
  • Your marketing emails that do not comply with the CAN-SPAM Act.
  • Someone is using your insecure network to send spams.
  • In some rare cases, the recipient's Barracuda Spam Firewall may be improperly configured.

Removal Process

The removal process from BRBL is manual. You have to fill a BRBL removal request form, and it should be processed within 24 hours. Steps to follow for getting your domain delisted from Baracuda BRBL:

  1. Detecting blacklisting of your domain
  2. Resolve issues causing the blacklist
  3. Fillup and submit BRBL delisting form

Detecting blacklisting of your domain

If yourself blacklisted in the BRBL, you would receive a bounce back email onto your sender email address with an SMTP error code. So based on that SMTP error code, you can detect and debug the vulnerabilities in your email habits.

To check the blacklisting, click on this link, enter your domain address or IP and click on check reputation. If you are blacklisted, you will the list of filters where you're listed. With this, we move on to the next step.

IP reputation checkup

For the Ip reputation checkup, you just have to put your IP address and submit. If you are listed you will be notified in the red letters


You will see in the notification a removal link saying click here.

After clicking on it you will be redirected to a removal form but before that. Resolve the issue that was the cause of you being listed on the list.

Domain reputation checkup

Domain reputation checkup is similar to the IP reputation checkup, you just have to put your IP address and submit.


If you are listed you will be notified in the red letters with the reason on why were you added.

In our example, the domain we put here was into the spam list.

You will find an email id provided so that you can use that contact the barracuda services for your domain removal.
But please try to fix the issue that has got you listed in the first place. Then request removal.
To resolve the issue you can follow the steps provided below.

Resolve issues causing the blacklist

Remember the mention of the bounce back email error we did in the previous section. You need to check the error code you receive with the bounce-back. 

According to Barracuda, you can also check the SMTP error code in their Barracuda Email Security Gateway panel. You need to login first. 

  1. Go to the BASIC > Message Log page. 
  2. Double click on the message you want to check.
  3. Check the Delivery Status field you might see Rejected and in the Delivery Detail you will find SMTP error code.

Here is a comprehensive list of some of the SMTP errors. It will consist of reasons due to which they have occurred from Barracuda, which is a result of emails mail servers rejecting your sent email:

  • 420 - Your email deferred due to suspicious content. You can try sending the emails after a while.
  • 421 - The service is not unavailable, connection closed.
  • 450 - Failed due to the user's mailbox being unavailable. Try again.
  • 451 - Aborted due to a server error. 
  • 452 - Aborted due to insufficient system storage.
  • 454 - Temporary error, TLS encoding is not available.
  • 500 - Command not recognized.
  • 501 - A syntax error with the sent arguments.
  • 502 - Command not implemented.
  • 503 - Bad sequence of commands.
  • 504 - Command parameter not implemented.
  • 530 - STARTTLS command not issued.
  • 535 - Authentication failure.
  • 550 - Failed due to the user's mailbox being unavailable. (These can occur due to it not being found, or the command was rejected due to policy reasons).
  • 551 - Recipient is not on the local server. In this case, the server gives a forwarding address, you should retry with this.
  • 552 - Aborted due to exceeded storage allocation.
  • 553 - Aborted due to the mailbox name being invalid.
  • 554 - Transaction failed.

Typically your emails landing to blacklist might have several reasons these are some of the basic steps you can take to fix them:

  1. Maintain a clean email list. Remove bounced/dropped and unsubscribed emails
  2. Improve customer engagement
  3. Check your email server configuration
  4. Check whether your email complies with the CAN-SPAM act

For more information on removal from the blacklist, you can check this link.

Fillup and submit the BRBL delisting form

Delisting from BRBL can be made through the Blacklist Removal form. 

The form consists of the following details you have to fill:

  1. Your domain IP to unlist
  2. Your email address for contact
  3. Your phone number for contact
  4. Reason for removal.


After the filling of the form, you should receive the email back from the [email protected] when your email is delisted successfully.

You can check your website again in the RBL lookup of the Barracuda blacklist again to confirm your delisting.


In this post, I have tried to discuss in detail about Barracuda Blacklist and their listing and delisting process. In case if you have some different views on the topic or have any queries, please feel free to share below in comments or write to dx(at)pepipost(dot)com.

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Hitesh Pandey💻

Full Stack Developer, Pepipost

🥑 Developer Evangelist | 🥇Email Geek

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