Source type

Nylas Source Configuration

Nylas sources receive notification webhooks, answer challenge checks, and verify x-nylas-signature over the raw body.

NYLASGET, POSTWebhook SecretEmail and messaging

Nylas webhooks documentation All source types

Nylas configuration

Create a Nylas source, keep GET and POST enabled, and provide the configured Webhook Secret values for provider signature. FastHook uses these settings to validate each Nylas delivery before it enters the routing workflow.

Source Type

NYLAS

Allowed methods

GET, POST

Authentication

Provider signature

Credential fields

Webhook Secret

Nylas source config

{
  "type": "NYLAS",
  "config": {
    "auth_type": "PROVIDER_SIGNATURE",
    "auth": {
      "provider": "NYLAS",
      "webhook_signing_secret": "provider-secret"
    },
    "allowed_http_methods": ["GET","POST"]
  }
}

GET validation before event POST

Nylas first calls the FastHook Source URL with a GET validation request.
FastHook verifies the configured Nylas token or challenge value and returns Nylas's expected 2xx response.
After validation succeeds, Nylas sends normal webhook events as POST requests to the same Source URL.

Nylas request contract

FastHook echoes GET ?challenge=... and verifies x-nylas-signature as HMAC-SHA256 hex over the raw body.

GETPOST

Special response: GET verification returns the exact challenge query value as text.

Nylas headers

Preserve challenge, x-nylas-signature when sending Nylas test deliveries. FastHook evaluates this request context before accepting the payload, so missing or modified values remain visible as rejected requests instead of routed events.

challenge

GET query parameter FastHook echoes for validation.

x-nylas-signature

HMAC-SHA256 hex signature over the raw body.

Nylas setup

Create a Nylas notification webhook with the FastHook Source URL.
Keep GET enabled so Nylas challenge validation can pass.
Paste the Nylas webhook secret into FastHook.