Editar /etc/redmine/«instancia»/configuration.yml:

default:
  # Outgoing emails configuration (see examples above)
  email_delivery:
    delivery_method: :smtp
    smtp_settings:
      address: "sistemas.tic.ufrj.br"
      port: "587"
      domain: "sistemas.tic.ufrj.br"
      authentication: :login
      user_name: "email@sistemas.tic.ufrj.br"
      password: "xxxx"
      enable_starttls_auto: true
      openssl_verify_mode: 'none'

Reiniciar o Apache HTTP:

# service apache2 restart