What is an email blacklist?

Last updated: April 25, 2017

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What is a blacklist?

A blacklist is a list of servers or domains that a blacklist operator has found to send spam. Not all blacklists are created equally. Some blacklists, such as Spamhaus, are reputable and can be more impactful. Whereas smaller blacklists such as Lashback, NoSolicitado, and Spam Cannibal usually have less impact. The impact that a blacklisting has on deliverability depends on the recipient server subscribing to the blacklist.

How does a blacklisting happen?

If a HubSpot customer sends an email campaign to a list that is outdated or contains purchased, scraped, or third party contacts, HubSpot’s shared email servers can become temporarily blacklisted. Blacklistings are caused by emailing spam traps.

Spam traps are addresses that once may have been valid but have since been repurposed by their provider for the sole purpose of tracking spam. Any email address that hasn’t engaged with an email for over one year has the potential to be a spam trap. Spam traps are also often placed on publicly available web pages and in the lists of data providers to report on senders who are scraping and emailing contacts without opt-in. You can learn more about spam traps here.

Because HubSpot uses shared servers, other senders are negatively affected by this behavior. For this reason, we take spam and our Acceptable Use Policy seriously.

What preventative steps can I take?

Ensure that your marketing strategy is following email deliverability best practices. Be sure to regularly maintain your contact database and remove contacts who have not engaged with your mail in the past year. If your sending list is outdated, you can run a permission pass campaign.

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