Reference
Configuration
Configure the network boundary, SMTP relay, senders, and runtime behavior.
Environment variables
| Variable | Purpose |
|---|---|
PRIVATE_BIND_IP | Host address used by the Compose port mapping; use 127.0.0.1 by default. |
SMTP_RELAY_VERSION | Container image tag used by Compose (for example, 1.1.2). |
API_KEY | Secret presented in X-API-Key; must contain at least 32 characters. |
SMTP_HOST | SMTP server hostname or IP address. |
SMTP_PORT | SMTP server port, typically 465 or 587. |
SMTP_AUTH | Whether SMTP authentication is enabled. |
SMTP_USERNAME | SMTP authentication username. |
SMTP_PASSWORD | SMTP authentication password or app password. |
SMTP_FROM_EMAIL | SMTP envelope sender used for every message. |
SMTP_FROM_NAME | Default display name for the visible sender. |
ALLOWED_FROM_DOMAINS | Comma-separated domains allowed in request-level from_email values. |
SMTP_SECURITY | Transport mode: ssl, starttls, or the supported unencrypted relay mode. |
SMTP_TIMEOUT_SECONDS | Connection and submission timeout in seconds. |
LOG_LEVEL | Application logging verbosity. |
DISABLE_DOCS | Disable the running API's interactive documentation when enabled. |
Transport security
Port 465 normally uses ssl, while port 587 normally uses starttls. Match the exact requirements of your provider; a port number does not automatically select a mode.
Envelope and visible senders
SMTP_FROM_EMAIL remains the SMTP envelope sender. A request-level from_email changes only the visible From header and must belong to an allowed domain. These addresses may be subject to different provider verification and bounce-handling rules.
Allowed domains
Separate multiple values in ALLOWED_FROM_DOMAINS with commas. Keep the list narrow. It is a local policy control, not proof that you own a domain and not a way to bypass provider authorization.