I'm building a small SaaS and need email delivery webhooks.

To track email delivery in a SaaS application, setting up webhooks keeps your database synchronized with the real-time status of sent emails.

Key Delivery Events to Track

Event Type	Triggers When	Primary Action
delivered	Recipient server accepts the message	Mark email as successfully delivered.
bounced	Hard (permanent) or soft (temporary) rejection	Suppress recipient email or notify user.
complained	Recipient marks email as spam	Immediately unsubscribe and add to suppression list.
opened / clicked	Recipient opens email or clicks a link	Update engagement metrics.

Core Architecture & Best Practices

┌─────────────────────┐       POST /webhooks/email        ┌─────────────────────────┐
│ Provider (Resend,   │ ─────────────────────────────────> │ Endpoint (Fast 200 OK) │
│ Postmark, SES, etc.)│                                   └────────────┬────────────┘
└─────────────────────┘                                                │
                                                                       ▼
                                                          ┌─────────────────────────┐
                                                          │ Queue / Async Worker    │
                                                          └────────────┬────────────┘
                                                                       ▼
                                                          ┌─────────────────────────┐
                                                          │ DB Status Update        │
                                                          └─────────────────────────┘

1. Keep Handlers Fast: Always return an immediate 200 OK. Offload parsing, database updates, and side effects to an async background queue (e.g., Redis/BullMQ, Celery, SQS) to avoid timing out the provider's HTTP request.
2. Signature Verification: Always verify HMAC signatures using the provider’s shared secret/signing key to prevent unauthorized payload injections.
3. Idempotency & Deduplication: Webhooks are delivered with at least once delivery semantics and may retry on failure. Store and check incoming event_id or message_id values before processing.