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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. Go to Mailing Lists and open the list you want to use as a suppression list (or create a new list first).
  2. Scroll down to the Suppression List section on the list's detail page.
  3. Toggle Is Suppression List to YES.
  4. Click Update.

The list is now a suppression list. Any address already on it — and any address added to it in the future — will be blocked from receiving mail.

Adding addresses to a suppression list​

Add addresses to the list the same way you would any mailing list — via CSV upload, the + Add button on the list's Recipients panel, 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.