# The synchronisation of a mailbox failed

Source: https://docs.emelia.io/docs/inbox-api/mailbox-sync-failed

Guide: [Inbox API](https://docs.emelia.io/docs/inbox-api.md)

Webhook event `mailbox.sync_failed`: Emelia sends an HTTP POST request to your URL.

Fired at each failed synchronisation attempt (deduplicated per mailbox and failure count). `deactivated: true` means synchronisation stopped and the mailbox must be reconnected (in Emelia, from the Emelia accounts page).

Registration: webhook subscriptions cannot be created with an API key, and Emelia has no screen for them yet: contact support.

## Headers

| Header | Description |
|---|---|
| `X-Maylee-Event` | Event name, same as `event` in the body. |
| `X-Maylee-Signature` | `t=<unix seconds>,v1=<hex HMAC-SHA256 of "<t>.<raw body>" keyed with the webhook secret>`. Reject deliveries older than 300 seconds and compare in constant time. |
| `User-Agent` | Fixed User-Agent of the delivery client. Do not use it to authenticate a delivery: verify the signature. |

## Payload

| Field | Type | Required | Description |
|---|---|---|---|
| `event` | any | yes |  |
| `createdAt` | string (date-time) | yes | Time of THIS delivery attempt (changes on retries). |
| `data` | object | yes |  |
| `data.mailboxId` | string | yes |  |
| `data.error` | string | yes |  |
| `data.failCount` | integer | yes |  |
| `data.deactivated` | boolean | yes |  |

```json
{
  "event": "mailbox.sync_failed",
  "createdAt": "2026-10-08T09:12:51.000Z",
  "data": {
    "mailboxId": "cmbxacme0000000000000001",
    "error": "Invalid credentials",
    "failCount": 3,
    "deactivated": false
  }
}
```