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Ten Tips to Prevent Email Blacklisting

-By and

Bad data has many negative and costly effects, but one of the most serious is being blacklisted. Email blacklisting can cause an organization’s communications to be blocked and made undeliverable, essentially branding the organization as a spammer and shutting down its ability to communicate with clients and other contacts. The effects of blacklisting can be long-lasting, time-consuming and quite expensive to fix.

How Email Blacklisting Happens

There are many ways an organization or IP address can be blacklisted.

  • Some email applications have a spam button that can be clicked if a user considers an email to be spam. If email recipients click the button, some Internet Service Providers (ISPs) may conclude that your email content or contact list quality is bad. Even clean lists of contacts who have opted in may still have problems if the email gets a spam complaint. The more complaints, the more likely an email will end up on a blacklist.
  • A significant number of bounced email addresses can be another indication to ISPs that your list may not be opted in, clean or current.
  • ISPs may block emails based on content if there are “spammy” words or phrases anywhere in the email, including the subject line.
  • A good email marketing list grows over time as new clients or prospects subscribe. Conversely, a list that grows substantially and quickly can be a red flag that a list may have been purchased.
  • ISPs and some corporate networks have their own set of criteria for blocking, using information from blacklists and content filters and moving flagged emails from inboxes to junk folders.

Tips to Avoid Email Blacklisting

Here are some useful tips to ensure that your lists and contact data are not putting you at risk for email blacklisting or violations of data privacy regulations. As an added benefit, following these tips can also improve the deliverability and effectiveness of your campaigns and provide additional ROI on your mailings and events:

  1. Never purchase lists or acquire lists from sources that can’t verify them.
  2. Routinely run email validation on contact lists to reduce the number of bad emails.
  3. Engage internal data stewards or outsourced data quality professionals to regularly research contacts and update or remove bad email addresses from your lists.
  4. Only add new contacts to mailing lists that are routinely utilized and maintained.
  5. Request and collect permission or express consent from contacts on your lists and ensure that your in-house contact data and list handling processes comply with data privacy regulations such as CASL, GDPR and CCPA.
  6. Routinely purge contacts who have had no activity for a set period such as the prior 12 months.
  7. Review and/or validate email addresses added to lists from sign-up forms to ensure the form submissions are done by real people who have a legitimate interest in your content. Spambots are automated computer programs that are built to find signup form code on your website or blog and submit fake information to your signup form. If your lists have these fake email addresses, you are more likely to be flagged as a spammer and your emails will be blocked. There are also more automated email verification processes such as ReCAPTCHA or hidden honeypot-capture fields that will help ensure malignant bots are not adding bad data to your lists. ReCAPTCHA shows an image of text that bots can’t read, so they can’t complete the form submission. Honeypot-capture fields are fields that are hidden on the form (so invisible to humans) and, if these fields are filled out when the form is submitted, that means that the submission was done by a web-crawling program and should not be accepted.
  8. Always deliver useful and relevant content in your emails, with an appropriate subject line, to ensure that your subscribers are getting what they signed up for.
  9. Respect recipients’ preferences and unsubscribe requests with processes that ensure your internal CRM users cannot overwrite preferences set by contacts.
  10. Monitor your sending IP addresses’ sending reputations. It’s important to know that depending on your provider, you may be sharing an IP with others and their own poor practices can affect your deliverability.

CLIENTSFirst regularly helps firms establish customized, effective and sustainable processes for contact and list management. Our CRM Success Consultants can help you build effective communications and put data management protocols in place to gain and track consent. Our Data Quality Team can make sure your data and lists are clean, correct and complete and help you develop a plan to maintain good quality data.

Be Proactive

Don’t wait until you get blacklisted to ensure your data, processes and content are meeting the necessary standards. Contact us at 404-249-9914 or for a complimentary mailing list email validation.


For more than a decade, the team at CLIENTSFirst Consulting has been helping professional services firms and other organizations successfully select and implement CRM and eMarketing systems to maximize value, adoption and return on investment. If you need help achieving CRM Success, please contact us at 404-249-9914 or


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