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Top 8 email blacklists

If you are a marketer, falling into an email blacklist could be one of your worst nightmares. Being blacklisted negatively impacts your marketing efforts and can take quite some time and efforts to come out of.

Many organizations, ISPs and networks maintain and share blacklists. As explained in our earlier post, different organizations may use different criteria to decide if your IP or domain should be blacklisted. You can find a detailed understanding on what are blacklists and how blacklists operate.

It’s important to understand that not all blacklists are important. Some carry more weight than others, so you should pay more attention to the heavyweights. Here is a comparison of blacklists you should worry about.

1. Composite Blocking List (CBL)

About: The Composite Blocking List (CBL) is not a list based on the volume of email from an IP address. Instead, it lists those IPs that behave like typical open proxies and dedicated spam bots, dictionary mail harvesters or stealthy, trojan-horse spamware. Special care is taken so as not to list shared IPs with legitimate use.

Who maintains it: Spamhaus

Nature of blacklist: It’s list of IPs. It lists individual IPs and not entire ranges.

How you can use it: It’s a simple lookup. You key in the IP address you want information on and the service will return the results.

How you’d fall into it: It lists only those IPs that have attempted email connections to their servers in a manner only used by infected IPs or IPs used in operation of botnets. It neither runs tests nor list open SMTP relays.

How to get out of it: There is a self-removal system. You can enter your IP details here and proceed for removal. They strongly advise correcting the problem, not just getting your IP delisted. If you delist without resolving the problem, you’ll back in the list pretty soon.

2. Spamhaus Block List (SBL)

About: Specialized teams of experts look for and redflag spam issues. They are spread over 10 countries to ensure a constant, round-the-clock to both list and delist spam issues. The SBL is queriable in realtime.

Who maintains it: Spamhaus

Nature of blacklist: It’s a database of blacklisted IP addresses. Spamhaus recommends not accepting emails from these IPs.

How you can use it: It’s free subject to Spamhaus DNSBL Usage Terms. Those who do not qualify for the free usage need to use Professional Use.

How you’d fall into it: One way to fall into the SBL is by sending unsolicited bulk email from an IP address.

How to get out of it: To begin with, confirm if you’ve been blacklisted.You can figure it out by submitting your IP address in a given box in Spamhaus blocklist removal center. If you’re blacklisted, the results of the query will tell you what to do next.

3. Exploits Black List (XBL)

About: The Exploits Black List (XBL) is a database of IP addresses that have been compromised by illegal exploits, viruses with spam engines and so on. Along with SBL and PBL, it forms the Zen list.

Who maintains it: Spamhaus

Nature of blacklist: It’s a database of blacklisted IP addresses that have been exploited by malicious attacks.

How you can use it: You can access go the Lookup and enter the IP address you wish to check.

How you’d fall into it: If your IP has been exposed to malicious attacks, including open proxies and trojan horses, the attackers would likely shoot thousands of emails using your IP. Then your IP will fall into the XBL.

How to get out of it: Since XBL basically lists IPs, you can feed your IP details into the Spamhaus checking system. If your IP is blacklisted, you will receive information on why your IP was blacklisted and what to do to get out of the list.

4. SenderScore

About: SenderScore tries to keep the email ecosystem safe by making sure IP addresses exhibiting spammy behaviour are blocklisted. Such activities depend on the system, but include details like whether the IP address sends out attachments that can infect recipients or malware that can potentially disrupt systems or networks.

Who maintains it: Returnpath

Nature of blacklist: It’s a list of IP addresses suspected of abusive behaviour

How you can use it: It’s a plain lookup service. You can check if an IP address is in the blocklist by submitting details of the IP address, the email address, company name, phone number and how you deploy marketing email, among other details.

How you’d fall into it: One Email campaigns sent through botnets and email authentication failures are the two of the major causes of an IP address falling into a blocklist. Other reasons include suspicious attachments, attachments sending virus and behaviours that are abusive of networks.

How to get out of it: You need to submit your IP address and request delisting from the blocklist. Delisting takes upto 24 hours to appear on live blocklists. Failure to correct the problem that led to your IP’s delisting will again lead the IP back into the blocklist.

5. Passive Spam Block List

About: Passive Spam Block List (shortened to PSBL, not to be confused with Spamhaus’s PBL: Policy Block List ) does not use any testing or scoring. Instead, it classifies IP addresses as spammers if they send emails to the spam traps maintained by PSBL.

Who maintains it: The PSBL is maintained using the Spamikaze software.

Nature of blacklist: It’s a list of IP addresses suspected of spamming.

How you can use it: Using it quite easy – you just check if your IP is blacklisted here by keying in your IP address in the query form. The result will tell you if you’re guilty of spamming. Usage is free.

How you’d fall into it: If your system sent an email to one of the spamtraps maintained by PSBL, your IP will be blacklisted.

How to get out of it: Since there are no testing or scoring involved, both falling into PSBL and getting out of it are relatively fast. If you’re a legitimate, one of the two things happen. You don’t send emails to the spam trap for a few weeks and your IP is automatically dropped off the list. Alternatively, you could submit a delist request manually.

6. SpamCop

About: SpamCop is a list of IP addresses. It is built through a number of sources and accepts both automated reports as well as submissions by users.

Who maintains it: Cisco systems.

Nature of blacklist: It’s a database of blacklisted IP addresses.

How you can use it: Using SpamCop is quite simple. You just need to feed the IP address you wish to verify.

How you’d fall into it: If you’ve sent a mass email, at least one of which went to SpamCop users, your IP address will likely be listed. Individual users, email service providers and SpamCop jointly use the SpamCop Blocking List (SCBL) to filter out unwanted email.  

How to get out of it: You cannot request removal – removal is time-based and automatic. SpamCop uses SCBL which is time-based. That means if end users stop reporting you to SpamCop, your IP address will be taken off the blocklist.

7. Barracuda Reputation Block List (BRBL)

About: In 2008, Barracuda Networks began maintaining and sharing the blocklist with others. Usage is free; however they reserve the right to reject registration requests to competitors or spammers.

Who maintains it: Barracuda Networks operates and maintains BRBL.

Nature of blacklist: It’s a database of IP addresses that have a proven record of sending spam.

How you can use it: There is  a Barracuda Lookup where you can key in the IP you wish to check. The Barracuda Reputation System will respond and tell you if the IP is listed as “poor”.

How you’d fall into it: If Barracuda Central detects that connecting machine is a node in a spam-generating botnet system or is an open proxy IP address sending the email, the IP address will be automatically added to the BRBL.

How to get out of it: To remove the IP from the blacklist, you need to enter into a Removal Request Form the following details: email server IP, email address and your phone number. Including a reason for removal is optional. Requests accompanied by valid explanations can expect delisting within 12 hours.

8. Invaluement

About: Invaluement blacklists were launched in 2007. It is a combination of 3 DNSBLs and sets up easily and quickly with email and spam filtering systems. They claim of having a very low False Positive rate.

Who maintains it: Invaluement, originally born as PowerView Systems.

Nature of blacklist: It’s a database of domains as well as IP addresses.

How you can use it: There’s a 7-day free trial, which will allow you the usage of all three anti-spam lists. You can choose either a direct query method or RSYNC method. Your pricing will depend on the method as well.

How you’d fall into it: IP addresses that send out only spam and those that send out spam most of the time can fall into this. In some cases, IP addresses that send out legitimate emails in low volume but are currently compromised may be listed for a short-duration. Catching snowshoe spammers is one of the major objectives.

How to get out of it: Place your removal requests here.To be delisted, you need to check whether an IP is blacklisted in the first place. It the IP is listed there, you can request for delisting it.

An additional tool: MultiRBL

We’ve kept this separate since this is not a database itself; it is a tool that helps you check where all you’re blacklisted.

About: MultiRBL is a DNSBL lookup and FCrDNS (iprev) checking tool. It is offered free of cost. Instead, it offers a free service by which you can check whether your IP or domain is blacklisted in any of the blacklists.

Nature of blacklist: It offers checking for both IPs and domains.

How you can use it: Just as elsewhere, you can simply type in your domain or the IP address  you are trying to learn more about. MultiRBL will return the results. Currently it runs your details through 59 tests (blacklists, whitelist, combined). The results of the search will be classified variously as Blacklists, Brown lists, Yellow list and so on.

How you’d fall into it and how to get out: It is important to understand that MultiRBL does not maintain its own database. Hence you can’t directly fall into it directly. If MultiRBL shows you listed somewhere, you need to study the policy of the respective blacklist to figure out how you can get out of it.

Concluding remarks on how to avoid blacklists

One of the most important rules to follow while trying to avoid blacklists is to make sure your mailing lists are clean. Email experts even suggest you develop a different strategy for recipients with poor engagement, to avoid being blacklisted.

Types of addresses matter too. For instance,role-addresses impact your deliverability. That’s because emails sent to role-addresses are often broadcast within a small team. Even if one of the team-member marks your email as spam, it would adversely impact the deliverability of emails in future.

Presence of accept-all addresses or invalid addresses on your mailing list will significantly increase the chances of ISPs believing you’re a spammer.

All this is bad for your email deliverability. To make sure your emails reach recipients and make it to the inbox, you should use a reliable email verifier tool. A good email address verification tool will help you clean your mailing list, maintain its hygiene and make sure you send out emails only to safe-to-send email addresses. As a result, you will be considered a legitimate, trusted sender.


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