version: '3' services: postfix: image: boky/postfix restart: unless-stopped environment: - RELAYHOST=${RELAYHOST} - RELAYHOST_USERNAME=${RELAYHOST_USERNAME} - RELAYHOST_PASSWORD=${RELAYHOST_PASSWORD} - POSTFIX_smtp_tls_security_level=${POSTFIX_smtp_tls_security_level} - ALLOWED_SENDER_DOMAINS=${ALLOWED_SENDER_DOMAINS} - MASQUERADED_DOMAINS=${MASQUERADED_DOMAINS} networks: - smtp_relay networks: smtp_relay: name: smtp_relay