Blacklists You REALLY Don’t Want To Be On as a B2B Enterprise Email Marketer

Chris Arrendale

3 minute read

Being put on a blacklist can cause major issues for your sending reputation. You will have stronger email delivery if you can verify that your emails are not on these blacklists. SpamCop, SORBS, and Spamhaus are only three of many spam reporting services on the web. Many blacklists will block IP’s and/or domains, so it’s important to understand email deliverability best practices while approaching blacklist-related issues.


The Spamhaus Project is an international organization, based in both London and Geneva, that tracks email spammers and spam-related activity.

The purpose of their organization is to create a “block” list of senders who have bad sending reputations. This list’s senders have shown poor sending practices by sending spam to Spamhaus’ partners or to their spam traps. Spamhaus will remember their IP and/or domain and publicly post them. Internet service providers and email servers use Spamhaus’ block list to reduce the amount of spam that reaches their users. You will have stronger email delivery if you can verify emails are not on these blacklists.

An IP or domain that’s put on Spamhaus has shown prolonged poor-sending practices. During this time, its B2B & B2C deliverability will both be significantly diminished. It’s used by Yahoo, AOL, and Hotmail, as well as dozens of ISPs in Europe and uncountable corporate email servers. No other blacklist comes close to affecting this volume, making Spamhaus a top priority for monitoring and remediating.

SORBS (Spam and Open-Relay Blocking System)

SORBS has a block list of over 12 million host servers known to disseminate spam, phishing attacks, and other forms of malicious email. Over 200,000 corporations worldwide use SORBS, making it a very significant concern for B2B senders.

SORBS uses partner spam reports and spam traps to identify and list IP addresses that show bad sending practices. A sender can also be put on SORBS from a recommendation by anyone. Fortunately, in an effort to reduce false positives (senders who are careless and not malicious), SORBS will remove offending IPs on request after 48 hours of no spam. However, repeat listings will lengthen the delisting time and SORBS will eventually stop delisting a repeat offender.

SORBS has a low false-positive rate, making it very popular, and therefore, a top priority for monitoring and remediation, especially for B2B senders.


SpamCop is an email spam reporting service. If you are sending unsolicited bulk or commercial emails, your recipients have the option to report your IP address to SpamCops analysis. This is where your IP address get on SpamCop’s block list. Therefore, an IP will be put on SpamCop from complaints of spam from that IP.

While filing spam reports, network administrators who use SpamCop will receive a list of IP addresses that are not allowed access into networks. So if you are sending email to an ISP that uses SpamCop from a computer whose IP is on their block list, your mail will be blocked and not deliver.

It takes upkeep to unblock your IP address from SpamCop. Mainly, because they handle blocking and unblocking on their own. If SpamCop continues to receive reports of spam originating from the networks you are responsible for, those networks will continue to be listed. If you can keep up with deliverability best practices , then you will be delisted by SpamCop automatically after 24 hours.


SpamCop, SORBS, and Spamhaus are only three of many spam reporting services on the web. To prevent from getting your IP or domain listed on a blacklist follow email deliverability best practices. Keep a clean list while updating hygiene continuously, stay on top of bounce logs, and keep an eye on the content you are sending out. Spam filters are continuously changing, therefore it’s good to have someone watching them, as it will prevent you from being blacklisted.

If you’re having deliverability problems, contact our deliverability experts.

Trendline Interactive

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About the Author(s)

Chris Arrendale

Founder of Inbox Pros (acquired by Trendline in July of 2018). Author of Deliverability Inferno. Certified expert and frequent speaker on the topics of data privacy, deliverability and compliance. BA in Poli-Sci/Soc from Emory, MS in Software Engineering & IT from Southern Polytechnic State University. A shoe and wine collection that’s the envy of pro athletes. Follow Chris on LinkedIn

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