What is an Email blacklist and how you can avoid it?

 In Email Deliverability

Have you ever wondered about your email being blacklisted, or even what it means? The Internet Service Provider (ISP) checks the sender’s reputation after it has cleared the SMTP server of the recipient. Email Marketers have found themselves at some point of time on at least one IP or domain blacklist. In a scenario where you find yourself on an IP blacklist or Email blacklist, it is imperative to take steps to get it delisted and improve your collection practices, sunsetting policies and eventually ensure deliverability. But first, let's see some definitions to help you understand better and take the necessary steps.

Important Questions and definitions :

What is an Ip address?
A unique string of numbers that identifies a specific server. For instance, Pepipost has several IP addresses that identify our server to ISP. Know more on IP address and its effects on your email deliverability..

What is a Domain:
Domain names represent a particular set of IP addresses. For example, pepipost.com is a domain name that identifies a definite set of IP addresses.

What is a Blacklist:
The complete list of blocked email addresses, IP addresses, and domains.


About Email Blacklist: Diving Deeper

This can be best understood from the Spamhaus Blacklist diagram.


 Spamhaus Blacklist diagram

Spam Traps:
ISPs use spam traps to identify email marketers who are not following the email best practices. From a broader perspective, spam traps fall in 4 major categories.

  • Pristine Spam Trap : These are essentially the email addresses which are invalid and we unable to opt into receiving emails. Pristine spam traps are used to identify marketers who follow poor list building strategies like scraping emails off a website or purchasing email lists. Hitting a pristine spam trap is more severe than any other spam trap.
  • Recycled Spam Trap : There are emails that were once valid but now have just been repurposed by the email service provider. If you send an email to these addresses they’ll typically bounce. There is however 3 checks you can follow to see if there is a recycled spam trap on your sending list which is as follows :
    • Your list is more than one year old.
    • You don't email your list frequently.
    • There are mistyped or invalid addresses (e.g., 2334ppo@flow.flow.flow.com) on your list
  • Goof Spam Traps : Sometimes there occurs an error in typing the recipients’ email address due to which it gets on some other recipients’ list. For example, if you type “Test@hitmail.com”  instead of “Test@hotmail.com”, you won’t have any clicks or opens on the addresses.

Spam Traps can hit your really bad. For instance, if you send the recycled spam traps your emails would simply reach the junk folder and for the pristine spam trap, you can be immediately blacklisted.  

Email Sender Reputation Assessment:

An email sender’s reputation is assessed on multiple factors including:

  • Track record: a history of sending emails in large volumes
  • Spam Score: how many email recipients have marked the Sender’s emails as Spam?
  • Sending history: how many times has the email bounced?
  • Blacklist history: does the sender’s IP address have previous blacklist history?
  • Email Engagement: How many recipients opened emails and clicked on links/content within the email?

What is an email blacklist and what you can do if your email address is blacklisted?

An email blacklist is a real-time database that checks whether an IP address is sending potential spam emails. Such blacklists exist with a goal to reduce email spam in the inbox. Ultimately, they exist to keep the email marketing environment clean.

If your recipients are marking your emails as spam, your IP address might end up on a blacklist. You will need to take immediate steps to be taken off the list.
You need to closely monitor spam rates, and verify your subscriber’s opt-in status. If there is any doubt about the opt-in validity, you may need to request opt-in again. Second, you need to improve engagement rates on your campaigns. It may be time to refresh your email strategy.

Check your IP address
Run your domain through blacklisting services to see if you have an issue. Take a look at these popular blacklists:

  1. Barracuda Reputation Block List : The BRBL is an open blacklist checker. You can also register on this list by providing the list of IP Addresses of your domain name servers (DNS) that will be sending queries. More information about the Barracuda Reputation Block list is available on the Barracuda Networks website.
  2. Spamhaus : The Spamhaus project is one of the most trusted blacklisting companies providing real-time anti-spam protection for internet networks worldwide. Visit their blacklist removal center to check whether your IP address is listed in the latest Spamhaus blocklists.
  3. Spamcop : SpamCop determines the origin of unwanted email and reports it to relevant Internet Service Providers. To get Spamcop reports for your IP addresses or for checking email deliverability problems, you can check their spam reporting centre.
  4. SURBL : SURBLs are lists of websites that have appeared in unsolicited messages. It is not a list of message senders. SURBL is a second stage filter that works with Spamhaus (zen.spamhaus.org) to find about 75% of the other unsolicited messages. Spamhaus can help identify 80 to 90% of unsolicited messages. For more information on this tier-2 email filter, visit http://www.surbl.org/
  5. Invaluement :  Invaluement is a compilation of 3 commercial anti-spam blacklists: ivmURI, ivmSIP and ivmSIP/24. This is similar to SURBL and sometimes called a domain blacklist. Invaluement indexes a list of domain names and IP addresses found within hyperlinks in spam emails. For more information, visit https://www.invaluement.com/

How to remove your IP addresses from a blacklist?

Use a blocklist checker tool to identify the list of DNBLs where your domain/IP is blacklisted. Once you know the list, submit a delisting request. First, you should change the behaviour that caused the delisting. If not, you will likely be delisted again. If your request is denied after the second or third attempt, it will be more difficult to be relisted.

At Pepipost, we know how important your reputation is, so our team will help you to monitor your email blacklists. Our 24/7 chat team is always ready and willing to help with any questions related to email blacklists.


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