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Understand email blocklists

Last updated: January 29, 2024

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A blocklist is a list of servers or domains that a blocklist operator has found to send spam. Not all blocklists are created equally. Some blocklists, such as Spamhaus, are reputable and can be more impactful. Whereas smaller blocklists such as Lashback, NoSolicitado, and Spam Cannibal usually have less impact and won't lead to bounces. The impact that a blocklisting has on deliverability depends on whether or not the recipient server uses the blocklist to filter spam.

How does a blocklisting 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If a HubSpot customer sends an email campaign to a list that is outdated or contains purchased, scraped, or third party contacts, HubSpot’s shared email servers can become temporarily blocklisted. Blocklistings 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 purchased to report on senders who are scraping and email addresses without opt-in. 

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

How does HubSpot respond to blocklistings?

As a recognized Email Service Provider, HubSpot's Email Deliverability team has relationships with points of contact at every major blocklist. The team actively monitors and resolves blocklistings by reputable and industry standard blocklist operators, such as Spamhaus and Spamcop. There are also blocklist operators the team won't request delisting from, because they won't cause bounces. These include blocklists that require payment for delisting IPs.

When a blocklisting event occurs, an Email Deliverability Consultant reaches out directly to the administrator of the blocklist to collect as much data as possible about the blocklisting event. This data is cross-referenced with email sent from HubSpot that matches the criteria to identify the specific email, and the specific sender that caused the blocklisting.

Once the email is identified, HubSpot's Email Deliverability Team alerts the sender, and the list containing the spam trap is opted out. The Email Deliverability team then ensures the customer takes steps to avoid future listings.

Please note: if your free HubSpot account causes HubSpot's shared email servers to be blocklisted, email sending in that account will be suspended and stay locked indefinitely. You may continue to access other tools in your account.

What preventative steps can I take?

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