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The Leadterra suppression list is a workspace-level blocklist that prevents any outbound message from being sent to a specified email address, regardless of which campaign it originates from. Once an address is suppressed, every campaign in your workspace will silently skip it — both at enrollment time and during active sends. This is the right tool for honoring unsubscribe requests, handling hard bounces, and respecting legal opt-out obligations.

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When to use suppression

Add an address to the suppression list in any of the following situations:
  • Unsubscribe requests — a prospect replies asking to be removed from your outreach or clicks an unsubscribe link.
  • Hard bounces — the address is invalid or permanently unreachable and continued sending would harm your domain reputation.
  • Legal requests — a contact invokes a right-to-erasure or do-not-contact request under GDPR, CAN-SPAM, or similar regulations.
  • Internal domains — your own company’s email domains, to prevent accidental self-sends during testing.
  • Competitor domains — addresses you’ve determined should never receive outreach from your workspace.

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Add to the suppression list

Call POST /v1/suppression-list with a JSON body containing an emails array. You can suppress one address or many in a single request. 
curl -X POST https://app.leadterra.co/v1/suppression-list \
  -H "Authorization: Bearer sk_live_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "emails": ["user@example.com"]
  }'
Leadterra confirms how many addresses were added to the list: 
{
  "result": {
    "suppressed": 1,
    "alreadySuppressed": 0,
    "total": 1
  }
}
alreadySuppressed counts addresses that were already on your list before this request — submitting a duplicate address is safe and does not produce an error.

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Bulk suppression

Pass multiple addresses in the emails array to suppress them all in a single API call. There is no practical limit to the number of addresses you can include per request. 
curl -X POST https://app.leadterra.co/v1/suppression-list \
  -H "Authorization: Bearer sk_live_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "emails": [
      "unsubscribe@example.com",
      "bounced@oldcompany.io",
      "legal-request@enterprise.com",
      "noreply@internalteam.co"
    ]
  }'

{
  "result": {
    "suppressed": 4,
    "alreadySuppressed": 0,
    "total": 4
  }
}
For very large suppression imports (tens of thousands of addresses), batch your requests into groups of 1,000 addresses each to ensure reliable processing.
Suppression is workspace-wide and affects every campaign, including ones that are currently running. Once an address is suppressed, it remains blocked until you manually remove it through the Leadterra dashboard. There is no automatic expiry — use suppression intentionally and keep a record of why each address was added.
Suppressed addresses are silently skipped during both enrollment and active sending. They will not appear in error responses or bounce reports — from the API’s perspective, they simply don’t exist as valid recipients in your workspace. This silent-skip behavior ensures suppression works seamlessly without disrupting bulk enrollment workflows.