In a perfect email marketers world you would know that when you hit ‘Send’ on your latest email newsletter it will reach the person it’s supposed to without any hassles or fuss. Unfortunately, this is the real world and things don’t quite work that way!
Sometimes your emails will never reach the inbox it was sent to, or they will bounce back to you for a variety of reasons. But the scariest reason and the one that the least people know what to do about is when your emails are blocked because you have been blacklisted. So today we are going to be explaining what blacklisting is, how you ended up on a blacklist and how you can find out if you’re on any of the blacklists out there.
Where does email blacklisting come from?
Firstly you need to understand why email blacklisting exists. For years everyone who had an email address had to deal with their inboxes being flooded by spam. In fact, at one stage statistics showed that over 70% of the emails people were receiving qualified as junk mail! So email providers began developing ways of sorting the legitimate mail from the spam, before it ever reached their users inboxes. And so in 1997, the very first email blacklist was created.
Everybody hates getting unsolicited emails, or spam in general and that is why any decent email platform has its own built in spam blocking or junk filtering system. But if your email address has somehow ended up in a spammer’s database then you will know that they are a persistent bunch. If at first they don’t succeed then they will try, try again – until ONE of their emails finally makes it to your inbox!
What exactly is an email blacklist?
But email providers have caught on to this fact, so instead of simply blocking emails from a single email address they will often block the whole domain or the IP address where an email originated. This means that the entire server where the email came from is blocked and you won’t be able to send ANY email – even if it is an email from your personal address! And unfortunately if you happen to share a server with spammers then you’re going to pay the price for their bad behaviour!
Now an email blacklist is a database of all the email addresses, domains or IP addresses that the list creator has for whatever reason classified as a spammer. The server receiving an email (i.e. your email provider) then searches this database to find information about the email senders reputation. Any emails that originate from an IP address or domain that has been flagged as a known source of spam will be blocked or bounced back to the sender.
Different types of blacklists
You get different types of blacklists, and the first is a private blacklist which is maintained by major ISP’s such as the ones used by Gmail, Yahoo, and Outlook.com. These lists tend to be a lot more strict about their spam filtering and there is unfortunately you won’t know that you have ended up on these lists until you start getting bouncebacks from those spam filters. Unfortunately there’s also no way to find out WHY you’re on the list!
The other blacklist that you need to be aware of is a public blacklist such as the ones maintained by SpamCop, Barracuda, Spamhaus, and others. These are blacklists that are available to the public so you can search their databases to find out of your domain or IP address is listed on them. And if you do find out that you’re listed then you can take steps to remedy the situation before you launch your next email campaign!
How can you end up on a private blacklist?
Different blacklists have different criteria for how an IP address or domain might end up being listed on it, but private blacklists are generally based on the content in an email, whether an email meets certain criteria and the volume of emails being sent to a particular domain or address. However because these lists are private there is no real way to find out exactly WHY certain IP’s or domains have ended up on them although you should make sure that:
- Your email contains the right balance of text and images
- Your email has an unsubscribe link and includes your physical address (this is required for CAN-SPAM compliance)
- Your email is not being sent from generic usernames such as marketing@, info@, sales@ and so forth
- Your Domainkeys and SPF have been set up properly
- There is not excessive punctuation or words that are classified as ‘spammy’ in your subject line
- You are splitting your lists into multiple smaller lists so that you don’t end up sending a huge batch of emails to the same domain (@exampledomain.com) all at once
How can you end up on a public blacklist?
The most common way of ending up on a public blacklist is when you send an email to a spam trap or honey pot. Spam traps are email addresses created by major blacklisting organizations and are there for the sole purpose of catching spammers. Pristine spamtraps are never used to sign up for or subscribe to anything; therefore any marketing mails they receive are unsolicited. But because they LOOK like legitimate email addresses, it is near impossible to identify them as spamtraps!
Some email addresses are repurposed as spamtraps, so they used to be a ‘traditional’ mailbox but are no longer in use. These kinds of spamtraps spend 12-18 months unsubscribing from email lists and sending ‘hard bounces’ telling legitimate marketers to stop sending them mail. However, if a prospect hasn’t engaged via email in over a year, find out if they still want to be on your email list. If they don’t reply, or reply in the negative – then they might have been repurposed so remove them!
How to find out if you have been publicly blacklisted
As we mentioned, there is no way to find out if you have been listed on a private blacklist until you start receiving bounce backs from that domain. This is not the case with public email blacklists and while you could visit every single database and search for your domain or IP address it would be much easier to use a service that simultaneously searches multiple databases. Some of the more popular tools include:
BlackListAlert: This site can check both your IP address’ and your domains reputation. All you do is type in the domain you’d like to know about (@domainexample.com) and the site generates an alphabetical list of all its block lists. If there is a green ‘OK’ next to the databases domain it means your domain is not listed on it, however if it is there the word ‘Listed’ will appear in red.
MX Toolbox: This is one of the more popular multiple blacklisting database search tools there are for checking the reputation of your IP address or domain. Firstly it displays an alphabetical list of all the blacklists it has checked along with your status on each of them. Secondly if it can find a reason for why you’re listed on a specific database it will display it in the ‘Reason’ column. And lastly, you can also pay for a monitoring service that will alert you if your IP address ever appears on any blacklist.
WhatIsMyIPAddress: you may have used this tool at some point to discover what your IP address is; however once you know that you can also use their handy Blacklist Check tool to find out of your IP address is on any lists. If there is a green tick next to the listed database domain, then you’re not listed on it. If the little icon is grey it means that they couldn’t check the database because it was offline, and if it is red then it means that you are listed.
MultiRBL: This is a free service that checks multiple databases by IPV4, IPV6 or by domain. It can be a little confusing to work through as it searches hundreds of databases some of which list you irrespective of whether your mail qualifies as spam or not. All results are color coded and will show whether your domain or IP address is unlisted, as well as if it is blacklisted, brown listed (also known as grey listed), yellow listed (known for sending SOME spam) or white listed.
The blacklists you should pay special attention to
There are dozens, if not hundreds of email blacklists out there and it is highly probable that you will at some point end up on at least one of them – especially if it is a smaller list! However there are a few email blacklists that you don’t want to end up on because they’re used by so many email platforms – meaning that your email marketing efforts will essentially be wasted! The most commonly used email block lists are:
Spamhaus Block List (SBL): This is a collection of databases with email addresses that Spamhaus recommends blocking emails from. It is a real time database that includes the IP addresses of a variety of spam sources including known spammers, spam gangs, spam operations and spam support services.
SpamCop (SCBL): SpamCop is a spam reporting service that gives its users the ability to report the IP addresses of anyone sending them unsolicited bulk mail (UBE) or unsolicited commercial mail (UCE) as spam. Because SpamCop relies solely on information from its users, it cannot determine if an email actually is spam or not.
Passive Spam Block List (PSBL): Any IP addresses listed on this database are ones that have sent an email to a spam trap, or have sent an email that cannot be identified as NOT being spam, or if the email has originated from an IP address that is not a known mail server.
Barracuda Reputation Block List (BRBL): This is a free DNS blacklist of IP addresses that are known to send spam.
URIBL: This is a collection of lists, not of IP addresses but of domains that have been identified as being used in spam emails, however the most important one is their Blacklist which you can find here.
SURBL: This is another blacklist of website domains that have been found in unsolicited emails.
Invaluement: The Invaluement DNS block list is used to block spam and unsolicited bulk email that is somehow slipping through traditional spam filters for whatever reason.
Now that you understand more about what blacklisting is and how it can happen to you, it is time to find out how you can get your IP address or domain removed from these lists, so check out our article on how to get off and stay off an email blacklist.