---
title: "Add Emails to Suppression List"
method: POST
path: "/v1/batch/suppression-lists/{listId}/emails"
tags: ["Cost Control"]
---

# Add Emails to Suppression List

`POST /v1/batch/suppression-lists/{listId}/emails`

Add emails to an existing suppression list. Emails are SHA-256 hashed server-side.

## Path parameters

- `listId` string, required

## Request body

- object
  - `emails` string[], required

## Response `200`

Emails added.

## Other responses

- `400` — Bad Request - The request was malformed or contains invalid parameters. **Common causes:** - Missing required fields - Invalid field format (e.g., malformed email) - Invalid JSON syntax - Invalid parameter values
- `401` — Unauthorized - Authentication failed. **Common causes:** - Missing X-API-Key header - Invalid or expired API key - Malformed API key

## Changes

- **2026-08-25** `1f289eff3a26` — 3 breaking
  - the `allOf[#/components/schemas/ErrorResponse]/errors/items/instance` response's property type/format changed from `string`/`uri` to `string`/`uri-reference` for status `400`
  - the `oneOf[#/components/schemas/InvalidApiKeyError]/allOf[#/components/schemas/ErrorResponse]/errors/items/instance` response's property type/format changed from `string`/`uri` to `string`/`uri-reference` for status `401`
  - the `oneOf[#/components/schemas/MissingAuthenticationError]/allOf[#/components/schemas/ErrorResponse]/errors/items/instance` response's property type/format changed from `string`/`uri` to `string`/`uri-reference` for status `401`

[Change history](https://skmtc.dev/leadmagic/apis/leadmagic-api/changes/v1/batch/suppression-lists/:listId/emails/post.md)

---

[API](https://skmtc.dev/leadmagic/apis/leadmagic-api.md) · [All operations](https://skmtc.dev/leadmagic/apis/leadmagic-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/leadmagic/leadmagic-api/revisions/1f289eff3a26/schema)