Nylas Source

When to use this source type

Choose the NYLAS source type when Nylas is the system sending webhook requests into FastHook. The source type keeps sender-specific setup close to the source: accepted methods, verification headers, challenge handling, and the exact credential fields are documented together so operators do not need to translate a generic HMAC form into a provider-specific contract.

FastHook verifies the source before accepted traffic is queued. A valid request is stored with verified: true, then connections route it to destinations. A bad signature, wrong token, or missing provider header is rejected as SOURCE_AUTH_FAILED. A method outside the allowed set is rejected as SOURCE_METHOD_NOT_ALLOWED.

FastHook configuration

In the dashboard, create a source, set Source Type to Nylas, keep Authenticate enabled when verification is required, and fill the fields below.

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

curl -X POST "https://api.fasthook.io/v1/sources" \
  -H "Authorization: Bearer $FASTHOOK_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "name": "Nylas production",
  "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

Some providers do not send normal event payloads first. They validate the callback URL or subscription contract before delivery starts, so keep the methods listed below enabled during setup.

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

HTTP methods

This source accepts only the methods listed below. Keep the set narrow so provider mistakes and accidental test calls are visible as rejected requests instead of being silently accepted.

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

Headers and verification

FastHook verifies the provider-specific values below before the request is accepted. The comparison is done against the raw inbound request body or the exact provider-specific signing input described here.

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

Provider setup checklist

1. Create a Nylas notification webhook with the FastHook Source URL.
2. Keep GET enabled so Nylas challenge validation can pass.
3. Paste the Nylas webhook secret into FastHook.
4. Open Nylas webhooks documentation when you need the provider's event list, dashboard steps, or retry policy.

Supported event types and payload shape

FastHook stores the original Nylas request before routing so filters, transformations, retries, and replay decisions can use the same provider evidence. Use stable headers and payload fields for routing rather than relying on receiver-side logs alone.

• Nylas webhook events should be routed by stable provider headers, event type fields, object ids, or payload paths that do not change between retries.
• Use provider delivery ids or business object ids as idempotency inputs before retrying or replaying traffic.

Troubleshooting

• No request appears: the provider is not calling the generated FastHook Source URL, the source URL was copied before saving, or the provider has not completed its setup validation.
• 405 method rejected: the provider sent a method outside GET, POST. Edit the source only if the provider documentation says that method is expected.
• 401 source auth failed: check the configured FastHook field, the provider signing secret, and the header names listed on this page.
• Signature mismatch: make sure the provider signs the same public Source URL it calls and that no proxy, parser, or manual resend changed the raw request body before FastHook received it.

Nylas source FAQ

Related docs

• Sources
• Source authentication
• Webhook signature validation
• Custom source responses
• Provider event routing