> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.usglobalmail.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.usglobalmail.com/_mcp/server.

# Service unavailable

Returned as `application/problem+json` with `code` `service_unavailable` and HTTP status `503`.

The service is temporarily unable to handle the request.

## Common causes

* Maintenance or overload.
* An upstream circuit breaker is open.

## How to resolve

* Retry after a short delay with backoff.

## Check system status

A `503` is a server-side failure, so it may reflect a known incident rather than a problem with your
request. Check the [System status page](/guides/core-concepts/system-status) — if there's an open
incident affecting the USGM API or USGM Core, the issue is on our side, so wait for it to resolve. If
everything is operational and the error persists, contact support with your `request_id`.

## Example

```json
{
  "type": "https://docs.usglobalmail.com/api/problems/service_unavailable",
  "title": "The service is temporarily unavailable.",
  "status": 503,
  "code": "service_unavailable",
  "request_id": "req_8f3c2a1b9d",
  "instance": "/v1/mails"
}
```

> **Note**
>
> This error is typically transient — safe to retry with exponential backoff.