Sinch Notifications API
Webhooks allow you to get updates in real-time about the status of your faxes. Webhooks are triggered by events such as the completion of a fax, and transmit information about the state of that fax to you via HTTP(S) or email. HTTP webhooks are multipart/form-data POST requests, and should be processed like form submissions. **Note:** When webhooks with Basic authentication credentials are shown in GET requests, the credentials are masked with `***`` symbols. It is not possible to retrieve previously-set credentials through the API. ## Setting up webhooks Depending on the type of webhook, you can configure the callback URLs in a few ways: **Incoming fax notification**: - On your [Fax service](https://dashboard.sinch.com/fax/services) in the dashboard. - Using the [API when configuring your service](https://developers.sinch.com/docs/fax/api-reference/fax/services/createnotificationwebhook). This is required to receive notifications about incoming calls to your Sinch number. **Fax completed notification**: - By including the `callbackUrl` property in the request body when you send a fax via the `/faxes` endpoint. ### Retries If a webhook fails, we will automatically retry sending the fax up to 16 times. There will be a delay before each retry, which increases as follows: | Retry number | Delay | Cumulative wait | | ------------ | ---------- | ------------ | | 1 | 5 minutes | 5 minutes | | 2 | 10 minutes | 15 minutes | | 3 | 20 minutes | 35 minutes | | 4 | 30 minutes | 1 hour 5 minutes | | 5-16 | 6 hours | up to ~3 days | ### IP Addresses Notifications are sent from the following IP addresses so you can add them to allowlists if necessary. | IP address | Description | | ---------- | ----------- | | 34.232.249.173 | use1 (East) | | 44.226.9.173 | usw2 (West) |