Email blacklists are real-time , automated databases that use specific criteria in determining if an IP is sending spam emails. Blacklists are also known as DNS-based Blackhole Lists.
There are a number of blacklists in the industry, including SpamCop, Spamhaus, SURBL and Barracuda Reputation Block List. The criteria each blacklist company uses for accepting inbound mail varies based on their own company determined standards. However, all of them can have a long-term damaging effect on your delivery rate.
How Do Blacklists Work?
At a high-level, anyone who sends an excessive amount of emails that are marked as spam, will be added to a list of offenders (a.k.a. blacklisted email senders) and will no longer be able to have their emails delivered to user’s inboxes.
For a more detailed understanding of how blacklists work, take a look at the Spamhaus diagram below. In the event an incoming email fails to meet the Spamhaus’ criteria for legitimate emails, the sender’s IP gets added to the list. There are some ISPs that use this data to make their conclusions on filtering the email messages sent on various IPs.
While Spamhaus doesn’t have any control over the delivery or placement of the messages, it does aide many ISPs in making their decision as to whether or not to deliver your message to your target user’s inbox or to send it directly to their spam folder.
How to Find Out If You’ve Been Blacklisted
Most of the email service providers send out some level of warning when your IP has been added to a blacklist. However, for a more robust audit, you can manually visit the top DNSBL lists periodically to ensure you haven’t been flagged somewhere along the way:
- Spamhaus – This is one of the top blacklisting companies providing thorough, real-time spam protection for internet networks around the world.
- Barracuda Reputation Block List (BRBL) – This is a free DNSBL of IP addresses notorious for sending out spam emails.
- SURBL – This is a second-tier filter which works with Spamhaus in identifying some of the most difficult unsolicited messages.
- SpamCop – SpamCop Blocking Lists (SCBLs) manage and share IP addresses that contained emails reported as spam by the SpamCop users.
How to Get Off Email Blacklisting
One of the main reasons for IPs to end up on a blacklist is the high rate of spam complaints from users. Should you discover that you’re on a list, you’ll want to contact the company immediately. All of these DNSBL websites listed above have detailed instructions on how to be removed from the blacklist. Being proactive always helps – so show the ISPs that you are trying your best to remedy your delivery challenges.
With deliverability experts like Mail Monitor on your side, you will have professional help navigating the ISP landscape.