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Suppression Lists

Any mailing list can be turned into a Suppression List. Once enabled, every address on that list is automatically blocked from receiving mail across all future orders - campaigns and one-time sends - including from sub-accounts.

When to use it​

  • A recipient has asked to be removed from your mailings
  • You have a do-not-contact list from your CRM
  • You want to honor opt-out requests at the account level so they're respected across every future campaign
  • Compliance with internal policies that require permanent exclusion for certain addresses

How to set up a suppression list​

  1. Open Mailing Lists in the sidebar and open the list you want to use as a suppression list (or create a new list first with Add Mailing List).
  2. Open the list's ⋮ menu and choose Advanced settings.
  3. In the Suppression list card, switch on Is suppression list and click Update.
  4. Confirm. The dialog explains that any recipient on the list won't be mailed in any order, from the main account or any sub-account, and that address fields must match exactly. Click Make it a suppression list.

The list is now a suppression list. It shows a red Suppression badge, and its name is shown in red on the Mailing Lists page. Any address already on it - and any address added to it in the future - will be blocked from receiving mail.

To stop using a list as a suppression list, switch Is suppression list off, click Update, and confirm with Stop suppressing.

Adding addresses to a suppression list​

Add addresses to the list the same way you would any mailing list - with Add recipients (CSV upload or manual entry), or integrations. There is no separate suppression-specific import flow.

Address fields must match exactly for suppression to take effect.

How suppression works​

When a send is processed, thanks.io checks every recipient against all suppression lists on the account. Any match is automatically skipped - the order completes for all other recipients, and suppressed addresses are counted as excluded in the order summary.

Suppression applies account-wide, including across all sub-accounts.

Tips & best practices​

  • Add opt-out requests to a suppression list immediately upon receipt.
  • Export your suppression list periodically as a backup.

Limits & gotchas​

  • Suppression applies account-wide - it cannot be scoped to a single campaign.
  • A suppressed address cannot receive any mail from your account until it is manually removed from the suppression list.
  • Address fields must match exactly - partial matches are not suppressed.