Email suppression lists

Your email service provider (ESP) maintains a list of suppressed email addresses, preventing you from messaging people who have experienced a hard bounce or logged a spam complaint. If you manage email deliveries through Customer.io (you don’t have a Custom SMTP server), you can view and manage these suppressions in Customer.io

How it works

Your email service provider (ESP) keeps a suppression list to ensure that they don’t send messages from servers that rejected them before, or people who explicitly do not want messages from you.

Your ESP adds an email address to its suppression list when:

  • A message intended to a person experiences a hard bounce.

    This means that either the recipient email address does not exist or the recipient email server blocked delivery.

  • A person lodges a spam complaint against a message.

See ESP suppressions in Customer.io

If you manage email deliveries through Customer.io, you can find your ESP suppression list in your workspace settings, under Settings > Workspace Settings > Email > Suppression List. You can manually remove addresses from this list. Please note that only Admins and Managers have access to view and manage the Suppression List within the workspace.

If you use a Custom SMTP server, you must manage your email provider’s suppression list directly through the ESP.

The email suppression list page
The email suppression list page

 ESP suppression is not the same as suppressing a person in Customer.io

People suppressed by the email service provider continue to exist in your workspace. They can receive messages through other channels and enter campaigns.

Go here to learn more about suppressing people in your workspace—this deletes them and ensures that you can’t reuse their IDs.

See ESP suppressions through the API

If you use Customer.io as your email service provider (ESP), you can look up and manage ESP-suppressions using our API.

  • You can look up suppressions by email address or by type (bounces, blocks, spam complaints, or invalid addresses).
  • You can also remove addresses from the ESP’s suppression list.
Copied to clipboard!
Is this page helpful?