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.

Your email service provider 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.

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.

If you use a Custom SMTP server, you must manage your email suppression list directly through your email service provider.

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 your 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.

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