class Mail::Message

def reply(*args, &block)
  self.class.new.tap do |reply|
    if message_id
      bracketed_message_id = "<#{message_id}>"
      reply.in_reply_to = bracketed_message_id
      if !references.nil?
        refs = [references].flatten.map { |r| "<#{r}>" }
        refs << bracketed_message_id
        reply.references = refs.join(' ')
      elsif !in_reply_to.nil? && !in_reply_to.kind_of?(Array)
        reply.references = "<#{in_reply_to}> #{bracketed_message_id}"
      end
      reply.references ||= bracketed_message_id
    end
    if subject
      reply.subject = subject =~ /^Re:/i ? subject : "Re: #{subject}"
    end
    if reply_to || from
      reply.to = self[reply_to ? :reply_to : :from].to_s
    end
    if to
      reply.from = self[:to].formatted.first.to_s
    end
    unless args.empty?
      if args.flatten.first.respond_to?(:each_pair)
        reply.send(:init_with_hash, args.flatten.first)
      else
        reply.send(:init_with_string, args.flatten[0].to_s.strip)
      end
    end
    if block_given?
      reply.instance_eval(&block)
    end
  end
end