postal/app/jobs/expire_held_messages_job.rb

class ExpireHeldMessagesJob < Postal::Job
  def perform
    Server.all.each do |server|
      messages = server.message_db.messages(:where => {
        :status => 'Held',
        :hold_expiry => {:less_than => Time.now.to_f}
      })

      messages.each(&:cancel_hold)
    end
  end
end