my ideal api

mail_server.rb

class MailingLst < PostalService::App
  config.some_config_var = ".."

  filter(:unsubscribed_users) do
    !list_members.include?(incoming.from)
  end

  filter(:subscribed_users) do
    list_members.include?(incoming.from)
  end

  unsubscribed_users do
    to "subscribe@#{config.domain}" do
      outgoing.subject = "SUBSCRIBED!"
      list_members << incoming.from
    end
  end

  subscribed_users do
    to "unsubscribe@#{config.domain}" do
      outgoing.subject = "UNSUBSCRIBED!"
      outgoing.body    = "Sorry to see you go!"
    end

    subject /*/ do
      outgoing.reply_to = CONFIGURATION_DATA[:default_sender]
      outgoing.bcc      = list_members.join(", ")
      outgoing.subject  = incoming.subject
      outgoing.body     = incoming.body.to_s
    end
  end
end