Most email marketers have found themselves on at least one IP or domain blacklist at some point. If you find yourself on a blacklist, it is a good idea to assess your address collection practices, evaluate your sunsetting policy, and then request a delisting at the relevant blacklist removal form.

The impact of having your IP or domain on a blacklist can range from being a small annoyance, to a complete showstopper for your email deliverability. Because deliverability is the primary concern for most email marketers, it is important to have some understanding of how blacklists function, and what you can do as a sender to reduce your risk of being blacklisted.

How Do Email Blacklists Work?

Most blacklists use networks of spam trap email addresses to identify IP addresses and domains that send unwanted commercial email. Spam traps are email addresses that the operator believes should not be receiving email from marketers, or any other source for that matter. For the most part, spam traps fall into one of three categories:

Recycled Spam Traps: These are email addresses that were once valid, but have been dormant long enough that they could not have engaged with any email in a long time (usually a year or more).

Typo Traps: These are email addresses that usually end up on recipient lists due to user error. Typing instead of Similar to recycled spam traps, these addresses never open or click any of the messages they receive. The anti-abuse community believes sending excessive amounts of mail to typo traps is indicative of poor list acquisition practices, and poor list hygiene.

Pristine Traps: These are email addresses and domains that have never been used to actively sign up to receive email. Pristine traps most commonly end up on mailing lists when senders purchase, rent, or scrape addresses.

Note: Some email blacklists also list domains and IP addresses based on user generated feedback and manual reporting of unsolicited emails.

Reducing Your Risk

There are several things that can be done to reduce this exposure:

Confirmed opt-in: Before adding a new recipient address to your active mailing list(s),send a confirmation email.


  • Only valid, engaged recipient addresses will be added to your mailing list.
  • Completely prevents typo traps, recycled spam traps, and pristine trap addresses from being added to your list.
  • Greatly increases open and click rates.
  • Reduces spam reports and unsubscribes.
  • Improved ROI per message sent.


  • Possible 20-30% reduction in marketing email opt-ins.
  • Extra “friction” in the sign-up process.

Engagement-Based Sunsetting: Remove email address from your mailing list if they do not open or click a message in some period of time. This time period varies depending on factors like your industry and sending frequency.


  • Removes “dead weight” from your emailing list.
  • Improves sending reputation by only sending to recently engaged recipients.
  • Improves ROI per message sent.
  • Reduces spam reports and unsubscribes.
  • Significantly reduces exposure to recycled spam traps and typo traps.
  • Improves brand reputation by reducing the number of emails sent to people that don’t want them.


  • Significant technical requirements of determining who is engaged.
  • Decreased list size.
  • Potentially leaving money on the table. (What percentage of long term non-engaged email recipients eventually convert to $$$?)

Real-Time Address Validation: Check email addresses at the point of signup for validity and common typos.


  • Reduction in common domain typos.
  • Reduction in pristine spam trap hits.
  • Reduces instances of fake email addresses.
  • Much less “friction” than confirmed opt in.
  • New signups tend to react positively to this kind of feature. (“Wow they caught my typo!”)


  • Licensing costs if using third party service.
  • Engineering and technical requirements if building your own verification logic.

Which Solution is Right for You?

The best solution for reducing your risk of ending up on a blacklist is different for every business model. Blacklists do not exist to make life more difficult for email senders. Because of the nearly unimaginable scale of the world’s spam problem, they are an unfortunate necessity.

Remember that the purpose of email blacklists is to prevent email from being sent to inboxes that did not recently opt-in to receive email with explicit and informed consent. This means that no single preventative measure will guarantee zero blacklistings. But it also means that if you are doing everything in your power to send email that people truly desire, it will make the process of getting delisted that much easier.

The deliverability guru in me wants to see senders adopt a confirmed opt-in model. Understandably, this can be a very tough sell for a lot of businesses. If confirmed opt-in is out of the question, senders should track the early engagement of new recipients and aggressively target non-engagers with winback or confirmation campaigns. This will greatly reduce the length of time you are sending emails to dead addresses.

Validating addresses at the point of signup can eliminate a lot of obviously bad domains and addresses. However, in the long run, this method fails to address the primary issue, which is sending email to recipients who, through non-engagement, have indicated that they are not interested in the messages they are receiving.

For more tips on how to avoid blacklists and other obstacles to your deliverability, check out our 2016 Email Deliverability Guide.

Luke is a deliverability expert with a passion for getting email to the inbox. His intimate understanding of the email ecosystem, email protocols, and marketing best practices allows him to provide data and insights that drive engagement and results from email programs both large and small.