---
title: "Enroll existing subscribers into a topic."
method: POST
path: "/topics/{topicId}/subscribe-existing-subscribers"
tags: ["Topics"]
---

# Enroll existing subscribers into a topic.

`POST /topics/{topicId}/subscribe-existing-subscribers`

## Request

- Base URL: `https://api.maildroppa.com` (the document declares no server; this is the origin it was published from)
- URL: `https://api.maildroppa.com/topics/{topicId}/subscribe-existing-subscribers`
- Auth: API key in header `X-API-Key`

Starts a background enrollment of all subscribers who can hold topic rows; reader opt-outs are never overridden.

## Path parameters

- `topicId` string, uuid, required

## Response `202`

Enrollment started or already running.

## Other responses

- `400`: Archived topic cannot be enrolled.
- `401`: Not Authorized
- `403`: Not Allowed
- `404`: Topic not found in this account.
- `409`: Another subscriber bulk operation is running.
- `428`: Accept the customer agreements in the app before using API keys.

---

[API](https://skmtc.dev/maildroppa/apis/maildroppa-api-beta.md) · [All operations](https://skmtc.dev/maildroppa/apis/maildroppa-api-beta/llms.txt) · [OpenAPI document](https://skmtc.dev/maildroppa/apis/maildroppa-api-beta/revisions/a9f5a3fd1fb0?raw)