Understand email blacklists

Last updated: March 4, 2020

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 and won't lead to bounces. The impact that a blacklisting has on deliverability depends on whether or not the recipient server uses the blacklist to filter spam.

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If a HubSpot customer sends an email campaign to a list that is outdated or contains purchased, scraped, or third party contacts, HubSpot’s shared email servers can become temporarily blacklisted.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 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 blacklistings?

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

When a blacklisting event occurs, an Email Deliverability Consultant reaches out directly to the administrator of the blacklist to collect as much data as possible about the blacklisting 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 blacklisting.

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 blacklisted, 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?