> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lettr.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Event Types

> Reference for all 22 Lettr webhook event types across message, engagement, and inbound relay categories, with payloads.

This page provides a complete reference of all 22 webhook event types that Lettr can send, organized into five categories.

## Message Events

These events track the delivery lifecycle of emails you send through Lettr.

### message.injection

Triggered when an email is accepted by Lettr and queued for delivery. This is the first event in any email's lifecycle.

### message.delivery

Triggered when an email is successfully delivered to the recipient's mail server. This is the most reliable indicator that the email reached its destination.

<Note>
  A delivery event means the recipient's mail server accepted the email. It does not guarantee the email reached the inbox — it could be filtered to spam or quarantined by the recipient's email provider.
</Note>

### message.bounce

Triggered when an email cannot be delivered. Bounces can be hard (permanent failure, such as a non-existent address) or soft (temporary issue, such as a full mailbox).

<Warning>
  Always handle hard bounces by removing the address from your mailing list. Continuing to send to hard-bounced addresses damages your sender reputation.
</Warning>

### message.delay

Triggered when email delivery is temporarily delayed. Lettr will continue retrying delivery automatically. Delays are common with large mail providers that throttle incoming connections.

### message.out\_of\_band

Triggered when an out-of-band bounce occurs. These arrive after the initial delivery appeared successful — the receiving server accepted the message initially, then later determined it could not be delivered and sent a separate bounce notification.

### message.spam\_complaint

Triggered when a recipient marks an email as spam. This is a serious signal that should trigger immediate suppression.

<Warning>
  Spam complaints severely impact your sender reputation. Always immediately suppress addresses that generate complaints and never send to them again. High complaint rates can result in your sending being suspended.
</Warning>

### message.policy\_rejection

Triggered when an email is rejected due to a policy rule before delivery was attempted. This could be due to content filtering, rate limits, or a configuration issue.

***

## Engagement Events

These events indicate that the recipient interacted with your email. Engagement events require open and/or click tracking to be enabled.

<Note>
  The engagement event category contains a known typo in the event names: `engagament` (missing an 'e'). This is intentional for backward compatibility and must be used exactly as shown.
</Note>

### engagament.open

Triggered when a recipient opens an email. Open tracking works by embedding a small invisible image in the email. Some email clients block images by default or prefetch them automatically, so open rates are an approximation rather than an exact count.

### engagament.initial\_open

Triggered on the first open of an email by a recipient. Subsequent opens of the same email generate `engagament.open` events instead.

### engagament.click

Triggered when a recipient clicks a link in an email. Requires click tracking to be enabled. Click data is generally more reliable than open data because it requires deliberate user action.

### engagament.amp\_open

Triggered when a recipient opens an email delivered in AMP format.

### engagament.amp\_initial\_open

Triggered on the first open of an AMP email by a recipient.

### engagament.amp\_click

Triggered when a recipient clicks a link within an AMP email.

***

## Generation Events

These events occur when there is a problem generating (assembling and preparing) a message for delivery.

### generation.generation\_failure

Triggered when something goes wrong while preparing the message for delivery. This is typically an infrastructure-level issue rather than something caused by your email content.

### generation.generation\_rejection

Triggered when a message is blocked during the generation phase — the point where the email is assembled and prepared for sending.

***

## Unsubscribe Events

These events track when recipients opt out of receiving your emails.

### unsubscribe.list\_unsubscribe

Triggered when a recipient unsubscribes via the List-Unsubscribe header, a one-click unsubscribe mechanism built into email standards.

### unsubscribe.link\_unsubscribe

Triggered when a recipient unsubscribes by clicking an unsubscribe link in the email body.

***

## Relay Events

These events are triggered by inbound email processing on your configured inbound domains.

### relay.relay\_injection

Triggered when an inbound email is received and queued for processing.

### relay.relay\_delivery

Triggered when an inbound email is successfully delivered to your configured endpoint.

### relay.relay\_rejection

Triggered when an inbound email is rejected.

### relay.relay\_tempfail

Triggered when delivery of an inbound email to your endpoint temporarily fails. Lettr will retry automatically.

### relay.relay\_permfail

Triggered when delivery of an inbound email to your endpoint permanently fails after all retry attempts are exhausted.

***

## Complete Event Type Reference

| Category    | Event Type                        | Label                   |
| ----------- | --------------------------------- | ----------------------- |
| Message     | `message.injection`               | Injection               |
| Message     | `message.delivery`                | Delivery                |
| Message     | `message.bounce`                  | Bounce                  |
| Message     | `message.delay`                   | Delay                   |
| Message     | `message.out_of_band`             | Out of Band             |
| Message     | `message.spam_complaint`          | Spam Complaint          |
| Message     | `message.policy_rejection`        | Policy Rejection        |
| Engagement  | `engagament.open`                 | Open                    |
| Engagement  | `engagament.initial_open`         | Initial Open            |
| Engagement  | `engagament.click`                | Click                   |
| Engagement  | `engagament.amp_open`             | AMP Open                |
| Engagement  | `engagament.amp_initial_open`     | AMP Initial Open        |
| Engagement  | `engagament.amp_click`            | AMP Click               |
| Generation  | `generation.generation_failure`   | Generation Failure      |
| Generation  | `generation.generation_rejection` | Generation Rejection    |
| Unsubscribe | `unsubscribe.list_unsubscribe`    | List Unsubscribe        |
| Unsubscribe | `unsubscribe.link_unsubscribe`    | Link Unsubscribe        |
| Relay       | `relay.relay_injection`           | Relay Injection         |
| Relay       | `relay.relay_delivery`            | Relay Delivery          |
| Relay       | `relay.relay_rejection`           | Relay Rejection         |
| Relay       | `relay.relay_tempfail`            | Relay Temporary Failure |
| Relay       | `relay.relay_permfail`            | Relay Permanent Failure |

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