Outbound Campaign API 500 on List Import

General Discussion
1

My current config is completely failing for bulk list imports via the Outbound API.

  • Endpoint: POST /api/v2/outbound/lists
  • SDK: Java 18.0.0
  • Payload: 5000 contacts with valid formatting

The request returns a 500 Internal Server Error immediately. No validation errors returned in the response body. This only happens when the contact count exceeds 4096.

2

It’s worth reviewing at the payload size limits for the outbound list endpoint. The system often rejects large JSON bodies with a 500 error instead of a 413. Try splitting the import into smaller chunks.

"max_contacts_per_request": 2000

This prevents timeout issues during high throughput scenarios.