Vars for my defaults/main.yml

postfix_conf:
  relayhost: 'smtp.mailgun.org:587'
  smtp_tls_security_level: 'encrypt'
  smtp_tls_note_starttls_offer: 'yes'
  smtp_sasl_auth_enable: 'yes'
  smtp_sasl_password_maps: "static:{{ mailgun_ssmtp_user }}:{{ mailgun_ssmtp_pass }}"
  smtp_sasl_security_options: 'noanonymous'

and in my tasks/main.yml

- name: Setup Postfix to support Mailgun relay
  import_role:
    name: linux-system-roles.postfix
  tags: [monitoring, mailgun]