compose.prod.yml

# Production-only overrides, combined with the shared compose.yml:
#
#     docker compose -f compose.yml -f compose.prod.yml ...
#
# The justfile does this with `env=prod` (e.g. `just run prod`).

services:
  # Outgoing mail relay for Nagios notifications. The application hands mail to
  # it on port 8025 (set MAILER_DSN=smtp://mailer:8025 in the production app/.env).
  #
  # Delivery model (configured via the repository-root .env):
  #   * SMARTHOST set   -> relay through that authenticated SMTP provider
  #                        (recommended). Because the spool is persisted on disk,
  #                        a transient provider outage is tolerated: queued mail is
  #                        retried until it gets through, so Nagios notifications
  #                        are never silently dropped.
  #   * SMARTHOST empty -> deliver directly to the recipients' MX servers.
  mailer:
    image: docker.io/devture/exim-relay:4.98-r0-4
    restart: unless-stopped
    # Same uid:gid as the other containers (the `exim` user inside the image),
    # so it can own its persistent spool directory below.
    user: 100:101
    environment:
      HOSTNAME: ${HOSTNAME}
      DISABLE_SENDER_VERIFICATION: 1
      # Upstream smarthost as `host::port` (e.g. smtp.example.com::587) plus the
      # authentication credentials. The relay uses opportunistic STARTTLS, so use a
      # STARTTLS port like 587 (implicit TLS on 465 is not supported by this image).
      # Leave SMARTHOST empty for direct-to-MX.
      SMARTHOST: ${SMARTHOST}
      SMTP_USERNAME: ${SMTP_USERNAME}
      SMTP_PASSWORD: ${SMTP_PASSWORD}
    volumes:
    # Persistent spool (store-and-forward queue) so undelivered mail survives
    # restarts and is retried. Created/owned by the `_var-exim-spool` just recipe.
    - ./var/container-data/exim-spool:/var/spool/exim:rw,cached