Email suppression lists

Updated

Email service providers (ESP) keep suppression lists to ensure they don’t send messages from servers that rejected them before or from people who explicitly do not want messages from you.

ESPs add an email address to their suppression lists when:

  • A message experiences a hard bounce.

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

  • A person sends a spam complaint against a message.

ESP suppression only prevents people from receiving emails. People with suppressed emails can still receive messages from other channels, start campaigns, and more.

If you want people with certain identifiers to never again receive messages or start workflows in your workspace, learn how to delete and suppress identifiers.

When a suppressed email can still receive emails

Email addresses suppressed based on message delivery can still receive emails from domains in your workspace not associated with the message delivery. For instance, if you send transactional messages with a different domain, this address could still receive order receipts.

However, suppression based on our ESP Suppression API will prevent the email address from receiving an email from any domain across your workspaces. So even if you send transactional messages with a different domain, this address wouldn’t be able to receive order receipts, password resets, or any email you send as a transactional message.

flowchart LR c{"Is the email address suppressed?"} -- yes, using ESP Suppression API --> f["Person won't receive any email across all domains in your account"] c -- yes, due to hard bounce or spam complaint --> h["Person won't receive email from domain the message came from"] c -- no --> g["Person can receive emails"]

Suppression based on message delivery

Email addresses suppressed based on message delivery (not our API) won’t receive emails from workspaces that use the domain associated with the suppression. For example, if you’re sending from sketcher.io in both Workspace A and Workspace B, and a hard bounce occurs from a message in Workspace A, we won’t send emails from sketcher.io to that recipient in both Workspace A and B. But they could still receive emails from another domain in your workspaces.

Suppression based on API

If you use Customer.io as your email service provider (ESP), you can look up and manage ESP-suppressions using our API. If you suppress an email address through this endpoint, that recipient won’t receive emails across any of your domains in your workspaces. This is more restrictive than how the ESP suppresses people based on message delivery.

View suppressions

If you manage email deliveries through Customer.io, you can find your ESP suppression list in Workspace Settings > Email > Suppression List.

 Only Account Admins and Workspace Admins have access to view and manage the suppression list within a workspace.

The email suppression list page
The email suppression list page

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

Remove emails from suppression list

To remove an email address suppressed by your ESP, follow these steps:

  1. Go to Workspace Settings > Email > Suppression List.
  2. Filter for and select the email.
  3. Click Unsuppress.

This action unsuppresses the email across all domains in your Customer.io account, not just the domain that sent the message that caused the suppression in the first place.

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