Delivery Events & Forensic Telemetry

Every activity logged in Emalc originates from an immutable EmailDeliveryEvent. This reference catalog documents all event strings, their triggers, the metadata collected during execution, and how to interpret raw SMTP response codes.

Event Naming Convention#

Emalc utilizes standard dot-notation prefixes for all system logs and webhook dispatches:

text

email.<lifecycle_state>

For example, when an email is accepted into a recipient's mailbox, the event string is email.delivered. When a recipient opens an email, the event string is email.opened.

Complete Event Catalog#

Standard Outbound Progression#

The standard lifecycle of a successfully dispatched and placed message:

Event String	Trigger Point	Forensic Data Collected	System Action
`email.queued`	Message accepted by Emalc dispatch pipeline	Queue priority, scheduled dispatch window	Holds email until MTA worker picks up job
`email.sent`	Handed off to global upstream MTAs	Outbound MTA host, TLS encryption handshake	Actively transmits payload toward recipient MX server
`email.delivered`	Destination mail server accepts email payload	Remote server response (`SMTP 250 2.0.0 OK`), latency ms	Marks delivery as successful

Temporary Delays & Permanent Rejections#

Events emitted when receiving servers reject or defer connection attempts:

Event String	Nature	Typical SMTP Code	Cause & Behavior
`email.delivered_delay`	Temporary Deferral	`421` / `451` / `452`	Destination server busy or applying greylisting. Emalc automatically retries with exponential backoff.
`email.soft_bounce`	Temporary Failure	`450` / `452`	Recipient mailbox is over quota or server temporarily unavailable. Retried for 72 hours.
`email.bounced`	Hard Failure	`550` / `551` / `553`	Permanent rejection (invalid email address, non-existent domain). Address is immediately suppressed.

Recipient Interactions#

Events emitted when a reader interacts with an email:

Event String	Interaction Type	Forensic Metadata Collected
`email.opened`	1×1 Tracking Pixel	Client IP address, approximate city & country, parsed User-Agent (OS, browser)
`email.clicked`	Link Click via Custom Tracking Domain	Exact destination URL, redirect latency, client IP, approximate location

Apple Mail Privacy Protection (MPP)

Apple Mail may pre-fetch tracking pixels on Wi-Fi before manual recipient interaction. Emalc's forensic logging records the proxy User-Agent string to help differentiate automated fetches from human opens.

Safety Protections & System Failures#

Events safeguarding sender reputation or indicating internal errors:

Event String	Trigger Reason	Reputation Impact
`email.unsubscribed`	Recipient clicked unsubscribe link in email footer	Neutral. Contact is instantly removed from active broadcast lists.
`email.complained`	Recipient marked email as spam (ISP Feedback Loop)	High. Contact is permanently blocked from receiving future emails.
`email.failed`	Network transport failure or invalid SMTP credentials	Diagnostic only. No reputation impact.
`email.rendering_failed`	Dynamic template compilation syntax error (e.g. invalid merge tag)	Diagnostic only. The email was not transmitted.

Understanding SMTP Status Codes#

When inspecting the Response Body in the Log Detail Sheet, destination servers return standardized three-digit SMTP response codes:

Code Range	Meaning	Example String	Recommended Action
`250`	Success	`250 2.0.0 OK Message accepted for delivery`	None. Message successfully reached destination server.
`421`	Service Unavailable	`421 4.7.0 Try again later, closing transmission`	No action required. Emalc retries connection automatically.
`451`	Local Processing Error	`451 4.3.0 Mail server busy or greylisting active`	Emalc will automatically retry dispatch with backoff.
`452`	Insufficient Storage	`452 4.2.2 Mailbox is full / quota exceeded`	Retried for 72 hours. If unresolved, marked as soft bounce.
`550`	Mailbox Unavailable	`550 5.1.1 User unknown / recipient does not exist`	Hard bounce. Emalc automatically suppresses recipient.
`554`	Transaction Failed / Policy	`554 5.7.1 Relay access denied or IP blocked`	Verify domain SPF/DKIM authentication and IP reputation.

Correlating Logs with Webhooks#

Emalc dispatches real-time webhooks for every recorded delivery event. You can correlate incoming webhook payloads directly with the Logs dashboard:

json

{
  "event": "email.delivered",
  "eventId": "a1b2c3d4-e5f6-7a8b-9c0d-1e2f3a4b5c6d",
  "emailId": "f9e8d7c6-b5a4-3210-fedc-ba9876543210",
  "recipient": "alex@customer.com",
  "timestamp": "2026-09-17T08:12:05.000Z",
  "smtpResponse": "250 2.0.0 OK Message accepted for delivery"
}

eventId: Matches the unique ID shown in the Log Detail Sheet.
emailId: Corresponds to the master message record visible in the Emails dashboard.

Automated Webhook Alerting

Use eventId to deduplicate incoming webhook streams and immediately correlate failed delivery logs with external telemetry systems like Datadog, Grafana, or Sentry.