### Install Posthorn from source

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Install the Posthorn binary using `go install`. Requires Go 1.25+.

```bash
go install github.com/craigmccaskill/posthorn/cmd/posthorn@latest
```

--------------------------------

### Run Posthorn CLI commands

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Examples of using the `validate` and `serve` subcommands for configuration validation and starting the HTTP listener.

```bash
posthorn validate --config /etc/posthorn/config.toml
posthorn serve --config /etc/posthorn/config.toml
```

--------------------------------

### Posthorn Startup Log Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/getting-started/quick-start.mdx

Example of structured log output from Posthorn upon successful startup, indicating the version, listening address, and configuration path.

```json
{"time":"2026-05-16T20:00:00Z","level":"INFO","msg":"posthorn starting","version":"v1.0.0","listen":":8080","config":"/etc/posthorn/config.toml","endpoints":1}
{"time":"2026-05-16T20:00:00Z","level":"INFO","msg":"endpoint registered","path":"/api/contact","transport":"postmark","recipients":1}
{"time":"2026-05-16T20:00:00Z","level":"INFO","msg":"http ingress listening","addr":":8080"}
```

--------------------------------

### Build Docs Site

Source: https://github.com/craigmccaskill/posthorn/blob/main/CONTRIBUTING.md

Install dependencies and build the documentation site. This command should be run from the 'site' directory.

```bash
cd site && npm ci && npm run build
```

--------------------------------

### Install Posthorn from a release artifact

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Download, extract, and install the pre-built binary for Linux AMD64 from a GitHub release.

```bash
curl -L -o posthorn.tar.gz \
  https://github.com/craigmccaskill/posthorn/releases/download/v1.0.0/posthorn-linux-amd64.tar.gz
tar -xzf posthorn.tar.gz
sudo install -m 0755 posthorn /usr/local/bin/posthorn
```

--------------------------------

### Serve Command with Config

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/cli.mdx

Starts the posthorn listener using a specified configuration file.

```bash
posthorn serve --config /etc/posthorn/config.toml
```

--------------------------------

### Start Posthorn Container (First Endpoint)

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/recipes/newsletter-signup.mdx

Start the Posthorn Docker container if this is the first endpoint being configured.

```bash
docker compose up -d
```

--------------------------------

### Verify Standalone Binary Installation

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/getting-started/installation.mdx

If you installed Posthorn as a standalone binary, use this command to check its version.

```bash
posthorn version
```

--------------------------------

### API Request Example (cURL)

Source: https://github.com/craigmccaskill/posthorn/blob/main/README.md

Example of how to send a POST request to the API endpoint using cURL. Includes setting authorization, content type, idempotency key, and JSON payload.

```bash
curl -X POST https://posthorn.yourdomain.com/api/transactional \
  -H "Authorization: Bearer $WORKER_KEY_PRIMARY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: reset:user-123:$(date -u +%FT%H)" \
  --data '{ \
    "to_override": "alice@example.com", \
    "subject_line": "Reset your password", \
    "message": "Click here: https://app.example.com/reset/abc" \
  }'
```

--------------------------------

### Verify Docker Installation

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/getting-started/installation.mdx

Run this command to check the version of the Posthorn Docker container and verify the installation.

```bash
docker run --rm ghcr.io/craigmccaskill/posthorn:latest version
```

--------------------------------

### Verify Posthorn installation

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Check the installed Posthorn version.

```bash
posthorn --version
# posthorn v1.0.0
```

--------------------------------

### Start and Monitor Posthorn Container

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/getting-started/quick-start.mdx

Start the Posthorn container in detached mode and follow its logs to observe startup messages and endpoint registration.

```bash
docker compose up -d
docker compose logs -f posthorn
```

--------------------------------

### Logrotate Configuration for Posthorn

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/reading-logs.mdx

Example logrotate configuration to manage the size and retention of Posthorn log files.

```text
# /etc/logrotate.d/posthorn
/var/log/posthorn.log {
    daily
    rotate 14
    compress
    missingok
    notifempty
    copytruncate
}
```

--------------------------------

### Build and Run Posthorn Server

Source: https://github.com/craigmccaskill/posthorn/blob/main/docs/manual-test.md

Builds the Posthorn application and starts it in the background, serving the configured endpoints. It then validates the configuration and waits for the server to be ready.

```bash
cd <repo-root>
go build -o /tmp/posthorn-manual/posthorn ./core/cmd/posthorn
cd /tmp/posthorn-manual
./posthorn validate --config posthorn.toml   # expect: exit 0
./posthorn serve --config posthorn.toml &
SERVE_PID=$!
sleep 1
```

--------------------------------

### Posthorn environment file

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Example environment file for Posthorn, used to set environment variables like API keys.

```bash
POSTMARK_API_KEY=your-postmark-server-token
```

--------------------------------

### Set Environment Variables with systemd

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/security/api-keys.mdx

Example of setting environment variables for Posthorn using systemd's EnvironmentFile directive.

```bash
# systemd
EnvironmentFile=/etc/posthorn/posthorn.env
```

--------------------------------

### Start Docker Compose and Monitor Posthorn Logs

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/recipes/gitea.mdx

Brings up the Docker services and tails the Posthorn logs to verify the SMTP listener registration and incoming mail.

```bash
docker compose up -d
docker compose logs -f posthorn
```

```json
{"msg":"smtp_listener registered","listen":":2525","transport":"postmark","smtp_users":0}
{"msg":"smtp ingress listening","addr":":2525"}
```

```bash
docker compose logs -f posthorn | grep -E 'smtp_|submission_'
```

--------------------------------

### Trusted Proxies Configuration

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/configuration/reference.mdx

Example of configuring trusted proxies using a mix of preset names and explicit CIDR ranges.

```toml
trusted_proxies = ["cloudflare", "10.0.0.0/8"]
```

--------------------------------

### Configure Transport API Key

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/security/api-keys.mdx

Example of configuring a transport API key using an environment variable placeholder in TOML.

```toml
# Transport credential
[endpoints.transport.settings]
api_key = "${env.POSTMARK_API_KEY}"
```

--------------------------------

### Run Posthorn Commands

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/getting-started/installation.mdx

Commands to validate the configuration file or start the Posthorn HTTP listener. Use the --config flag to specify your TOML configuration.

```bash
posthorn validate --config posthorn.toml   # check the config without serving
posthorn serve --config posthorn.toml      # start the HTTP listener
```

--------------------------------

### Prepare Working Directory

Source: https://github.com/craigmccaskill/posthorn/blob/main/docs/manual-test.md

Creates a new directory for the manual test and navigates into it. This is the first step in setting up the test environment.

```bash
mkdir -p /tmp/posthorn-manual
cd /tmp/posthorn-manual
```

--------------------------------

### Example of From Address with Placeholder

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/configuration/environment-variables.mdx

Demonstrates using an environment variable for the 'from' address, allowing it to change across different environments while maintaining a consistent configuration structure.

```toml
from = "Contact <${env.NOREPLY_ADDR}>"
```

--------------------------------

### Build Posthorn from Source

Source: https://github.com/craigmccaskill/posthorn/blob/main/README.md

Instructions to clone the Posthorn repository, navigate to the core directory, build the binary, and verify the version. Requires Go 1.25+.

```bash
git clone https://github.com/craigmccaskill/posthorn
cd posthorn/core
go build -o /tmp/posthorn ./cmd/posthorn
/tmp/posthorn version
```

--------------------------------

### Run Test Suite and Build Binary

Source: https://github.com/craigmccaskill/posthorn/blob/main/CONTRIBUTING.md

Execute the test suite with race detection and build the Posthorn binary. Ensure you are in the 'core' directory before running tests.

```bash
cd core && go test -race ./...

go build -o posthorn ./cmd/posthorn
./posthorn version
```

--------------------------------

### Example Weekly Umami Digest Email

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/recipes/umami.mdx

This is an example of the email digest that will be sent. It includes key metrics from Umami analytics for a specific week.

```text
Subject: Weekly Umami digest for example.com (2026-W22)

Pageviews:    12,847
Visitors:     3,201
Visits:       4,886
Bounce rate:  41.2%
Avg time:     1m 38s
```

--------------------------------

### Posthorn Starting Event

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Log event emitted once at the start of the Posthorn process. Includes version, listening address, configuration path, and number of endpoints.

```json
{
  "level": "INFO",
  "msg": "posthorn starting",
  "version": "v1.0.0",
  "listen": ":8080",
  "config": "/etc/posthorn/config.toml",
  "endpoints": 2
}
```

--------------------------------

### Complete Posthorn Configuration Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/configuration/reference.mdx

This TOML configuration demonstrates how to set up multiple HTTP endpoints for contact forms and transactional APIs, as well as an SMTP listener for services like Ghost or Gitea. It includes logging, endpoint-specific settings, transport configurations, rate limiting, and SMTP listener options.

```toml
# Two HTTP endpoints (a contact form + a transactional api-mode endpoint)
# plus an SMTP listener for Ghost/Gitea/etc.

[logging]
level = "info"
format = "json"

[[endpoints]]
path = "/api/contact"
to = ["alerts@example.com"]
from = "Contact Form <noreply@example.com>"
required = ["name", "email", "message"]
email_field = "email"
honeypot = "_gotcha"
allowed_origins = ["https://example.com", "https://www.example.com"]
max_body_size = "64KB"
trusted_proxies = ["cloudflare"]
csrf_secret = "${env.CSRF_SECRET}"
csrf_token_ttl = "30m"
subject = "Contact: {{.name}}"
body = """
From: {{.name}} <{{.email}}>

{{.message}}
"""
redirect_success = "/thank-you"
redirect_error = "/contact?error=1"

[endpoints.transport]
type = "postmark"

[endpoints.transport.settings]
api_key = "${env.POSTMARK_CONTACT_KEY}"

[endpoints.rate_limit]
count = 5
interval = "1m"

# ---

[[endpoints]]
path = "/api/transactional"
to = ["fallback@example.com"]
from = "App <noreply@example.com>"
auth = "api-key"
api_keys = ["${env.WORKER_KEY_PRIMARY}", "${env.WORKER_KEY_BACKUP}"]
idempotency_cache_size = 5000
required = ["subject_line", "body"]
subject = "{{.subject_line}}"
body = "{{.body}}"

[endpoints.transport]
type = "resend"

[endpoints.transport.settings]
api_key = "${env.RESEND_API_KEY}"

[endpoints.rate_limit]
count = 100
interval = "1m"

# ---

[smtp_listener]
listen = ":2525"
require_tls = true
tls_cert = "/etc/posthorn/cert.pem"
tls_key = "/etc/posthorn/key.pem"
auth_required = "smtp-auth"
allowed_senders = ["*@example.com"]
max_recipients_per_session = 10
max_message_size = "1MB"

[[smtp_listener.smtp_users]]
username = "ghost"
password = "${env.GHOST_SMTP_PASSWORD}"

[smtp_listener.transport]
type = "postmark"

[smtp_listener.transport.settings]
api_key = "${env.POSTMARK_API_KEY}"
```

--------------------------------

### Build Posthorn from the repository

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Clone the Posthorn repository and build the binary locally.

```bash
git clone https://github.com/craigmccaskill/posthorn
cd posthorn
go build -o posthorn ./core/cmd/posthorn
```

--------------------------------

### 500 Internal Server Error Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/response-codes.mdx

This is an example of a 500 Internal Server Error response. It indicates a Posthorn-internal failure, such as a template rendering issue or another server-side error not caused by the upstream service. The body is plain text.

```http
HTTP/1.1 500 Internal Server Error
Content-Type: text/plain; charset=utf-8

submission could not be processed
```

--------------------------------

### Create Project Directory

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/getting-started/quick-start.mdx

Create a new directory for your Posthorn project and navigate into it.

```bash
mkdir posthorn-test && cd posthorn-test
```

--------------------------------

### send_retry_succeeded Log Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Logs when a retried submission attempt is successful.

```json
{
  "level": "INFO",
  "msg": "send_retry_succeeded",
  "submission_id": "...",
  "endpoint": "/api/contact",
  "transport": "postmark"
}
```

--------------------------------

### Posthorn Startup Log Output

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/recipes/multi-form-site.mdx

Example log output from Posthorn after a restart, showing successful registration of endpoints and the HTTP ingress listener. This confirms that Posthorn is running and ready to accept form submissions.

```json
{"time":"...","level":"INFO","msg":"endpoint registered","path":"/api/contact","transport":"postmark","recipients":1}
{"time":"...","level":"INFO","msg":"endpoint registered","path":"/api/feedback","transport":"postmark","recipients":1}
{"time":"...","level":"INFO","msg":"endpoint registered","path":"/api/careers","transport":"postmark","recipients":1}
{"time":"...","level":"INFO","msg":"http ingress listening","addr":":8080"}

```

--------------------------------

### submission_sent Log Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Logs when the transport successfully accepts a message submission.

```json
{
  "level": "INFO",
  "msg": "submission_sent",
  "submission_id": "...",
  "endpoint": "/api/contact",
  "transport": "postmark",
  "latency_ms": 312,
  "transport_message_id": "abc123-postmark-id"
}
```

--------------------------------

### Posthorn Application Lifecycle

Source: https://github.com/craigmccaskill/posthorn/blob/main/spec/03-architecture.md

Describes the sequence of operations from application startup, configuration loading, request handling setup, to graceful shutdown upon receiving termination signals.

```go
1. main.go: parse CLI flags (subcommand: serve | validate)
2. config.Load(path): read TOML, resolve ${env.VAR}, validate schema
3. For each endpoint in config:
     a. Construct transport (Postmark client with API key)
     b. Compile templates (subject, body)
     c. Construct rate limiter
     d. Construct core.Handler with all of the above
4. Build http.ServeMux mapping each endpoint path to its core.Handler
5. http.Server.ListenAndServe()
6. On SIGTERM/SIGINT:
     a. Stop accepting new connections (server.Shutdown)
     b. Drain in-flight requests up to 10s per-request timeout
     c. Exit 0
   On second signal: forced exit
```

--------------------------------

### HTTP Success Response (JSON)

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/http-api.mdx

Example of a successful submission response with a JSON body.

```http
HTTP/1.1 200 OK
Content-Type: application/json

{
  "status": "ok",
  "submission_id": "7f2c84d6-9b1e-4c2f-a3b8-1a2b3c4d5e6f"
}
```

--------------------------------

### Posthorn Template Syntax Examples

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/features/templating.mdx

Illustrates common Go text/template syntax used in Posthorn for email templating, including variables, pipes, conditionals, and comments.

```text/template
{{.name}}
```

```text/template
{{.email | html}}
```

```text/template
{{if .urgent}}!!!{{end}}
```

```text/template
{{if eq .category "bug"}}
```

```text/template
{{/* this is a comment */}}
```

--------------------------------

### jq Queries for Ad-hoc Log Analysis

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Examples of using jq with Docker logs for ad-hoc analysis of Posthorn logs. These queries demonstrate tailing logs, filtering by level, analyzing latency, and searching for specific IDs.

```bash
# Tail and pretty-print
docker logs -f posthorn | jq .
```

```bash
# All failures from the last hour
docker logs --since 1h posthorn | jq 'select(.level=="ERROR")'
```

```bash
# Latency P99 over the last 1000 sent submissions
docker logs --tail 10000 posthorn \
  | jq -s 'map(select(.msg=="submission_sent")) | sort_by(.latency_ms) | .[-10:]'
```

```bash
# Find a specific submission across all log lines
docker logs posthorn | jq 'select(.submission_id=="7f2c84d6-9b1e-4c2f-a3b8-1a2b3c4d5e6f")'
```

```bash
# Find a specific SMTP session across all log lines
docker logs posthorn | jq 'select(.session_id=="...")'
```

--------------------------------

### submission_failed Log Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Logs when a submission fails terminally due to errors, timeouts, or exhausted retries.

```json
{
  "level": "ERROR",
  "msg": "submission_failed",
  "submission_id": "...",
  "endpoint": "/api/contact",
  "transport": "postmark",
  "error": "postmark: 422 The 'From' address is not a valid Sender Signature.",
  "form": {
    "name": "Alice Smith",
    "email": "alice@example.com",
    "message": "..."
  },
  "latency_ms": 287
}
```

--------------------------------

### HTTP Success Response (Redirect)

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/http-api.mdx

Example of a successful submission response when a redirect is configured and HTML is preferred.

```http
HTTP/1.1 303 See Other
Location: /thank-you
```

--------------------------------

### Path Conflict Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/configuration/endpoints.mdx

Illustrates a configuration error where two endpoints are defined with the same path, which will be rejected during validation.

```toml
[[endpoints]]
path = "/api/contact"

[[endpoints]]
path = "/api/contact"   # ← rejected: duplicate path
```

--------------------------------

### Kubernetes: All Pods in Deployment (Multi-Replica)

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/reading-logs.mdx

Stream logs from all pods in a multi-replica deployment, with prefixes, using `kubectl logs -f --selector app=posthorn --max-log-requests=10 --prefix`.

```bash
kubectl logs -f --selector app=posthorn --max-log-requests=10 --prefix
```

--------------------------------

### Manage Posthorn systemd service

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/binary.mdx

Commands to reload systemd, enable and start the Posthorn service, and check its status.

```bash
sudo systemctl daemon-reload
sudo systemctl enable --now posthorn
sudo systemctl status posthorn
```

--------------------------------

### Registering a Transport

Source: https://github.com/craigmccaskill/posthorn/blob/main/spec/03-architecture.md

Demonstrates the transport registry pattern where each transport registers itself with a type, validator, and factory function during initialization.

```go
transport.Register("resend", resend.ValidateConfig, resend.New)
transport.Register("mailgun", mailgun.ValidateConfig, mailgun.New)
transport.Register("ses", ses.ValidateConfig, ses.New)
transport.Register("smtpout", smtpout.ValidateConfig, smtpout.New)
```

--------------------------------

### submission_failed Log Example with form_fields

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Shows the structure of a submission_failed log when the 'form' field is redacted to 'form_fields' for privacy.

```json
{
  "...": "...",
  "form_fields": ["name", "email", "message"]
}
```

--------------------------------

### send_retry_failed Log Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Indicates that a retry attempt for a submission also failed, marking the end of retries for this submission.

```json
{
  "level": "INFO",
  "msg": "send_retry_failed",
  "submission_id": "...",
  "endpoint": "/api/contact",
  "transport": "postmark",
  "error": "postmark: 422 The 'From' address is not a valid Sender Signature."
}
```

--------------------------------

### Standalone Binary: Live JSON Pretty-Print

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/reading-logs.mdx

Pipe the output of `posthorn serve` to `jq .` for pretty-printed JSON logs.

```bash
posthorn serve --config posthorn.toml | jq .
```

--------------------------------

### Display Posthorn CLI Help Information

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/cli.mdx

Use the `help` command to view general usage instructions and a list of available subcommands. This command is aliased to `--help` and `-h`. Subcommand-specific help is not available separately.

```bash
$ posthorn help
posthorn — outbound mail gateway

Usage:
  posthorn serve     [--config <path>] [--listen <addr>]
  posthorn validate  [--config <path>]
  posthorn version
  posthorn help

Examples:
  posthorn serve --config /etc/posthorn/config.toml
  posthorn validate --config ./posthorn.toml
```

--------------------------------

### send_retry_scheduled Log Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/log-format.mdx

Indicates that a transport returned a retryable error and Posthorn is preparing to retry the submission after a delay.

```json
{
  "level": "INFO",
  "msg": "send_retry_scheduled",
  "submission_id": "...",
  "endpoint": "/api/contact",
  "transport": "postmark",
  "class": "transient",
  "status": 503,
  "delay": 1000000000
}
```

--------------------------------

### Create Posthorn Directory

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/recipes/contact-form.mdx

Creates a directory for the Posthorn deployment and navigates into it.

```bash
mkdir -p posthorn && cd posthorn
```

--------------------------------

### Set Environment Variables Directly

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/security/api-keys.mdx

Example of setting an environment variable directly when running Posthorn from the command line.

```bash
# direct
POSTMARK_API_KEY=abc123 posthorn serve --config ...
```

--------------------------------

### Set Environment Variables with Docker Compose

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/security/api-keys.mdx

Example of setting environment variables for Posthorn using Docker Compose.

```bash
# Docker Compose
docker compose --env-file .env up -d
```

--------------------------------

### Standalone Binary: Append to File

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/deployment/reading-logs.mdx

Run the Posthorn server and redirect its stdout and stderr to a log file using `>> /var/log/posthorn.log 2>&1 &`.

```bash
posthorn serve --config posthorn.toml >> /var/log/posthorn.log 2>&1 &
```

--------------------------------

### API Mode Response Example

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/reference/http-api.mdx

This is a successful response format for API mode requests. It includes the status and submission ID.

```http
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8

{"status":"ok","submission_id":"..."}
```

--------------------------------

### Configure SMTP User Password

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/security/api-keys.mdx

Example of configuring an SMTP user password using an environment variable placeholder in TOML.

```toml
# SMTP user password
[[smtp_listener.smtp_users]]
username = "ghost"
password = "${env.GHOST_SMTP_PASSWORD}"
```

--------------------------------

### Common SES Gotchas and Fixes

Source: https://github.com/craigmccaskill/posthorn/blob/main/site/src/content/docs/configuration/transports/ses.mdx

Lists common issues encountered when using SES, their likely causes, and recommended solutions.

```markdown
## Common gotchas

| Symptom |
|---|---|
| `4xx MessageRejected: Email address not verified` | Sandbox mode + unverified recipient |
| `403 SignatureDoesNotMatch` | Clock skew — SigV4 timestamps must be within 15 minutes of AWS's clock |
| `403 InvalidClientTokenId` | Access key ID wrong, or IAM user disabled |
| Mail goes to recipient's spam | DKIM CNAMEs not published, or DMARC alignment wrong |
```