My local testing I'm using

```yaml

  mail-service:
    container_name: mail-service
    image: docker.io/metabrainz/mb-mail-service:main
    environment:
      - APP_SMTP_PORT=1025
      - APP_SMTP_HOST=smtp-relay
    depends_on:
      - smtp-relay
    ports:
      - 3000:3000
    restart: unless-stopped

  smtp-relay:
    # This would be an actual SMTP relay in production
    image: axllent/mailpit
    container_name: smtp-relay
    restart: unless-stopped
    # volumes:
    #   - ./data:/data
    ports:
      - 8025:8025
      - 1025:1025
    expose:
      - "8025"
    environment:
      MP_MAX_MESSAGES: 5000
      # MP_DATABASE: /data/mailpit.db
      MP_SMTP_AUTH_ACCEPT_ANY: 1
      MP_SMTP_AUTH_ALLOW_INSECURE: 1
```

Plus

```perl
sub SMTP_SERVER { 'smtp-relay:1025' }
sub MAIL_SERVICE_BASE_URL { 'http://mail-service:3000' }
```