mail-archiver.rb

#!/usr/bin/env ruby

require 'pathname'
require 'mail'

class Archiver
  attr_reader :maildir, :time

  def initialize(maildir)
    @maildir = maildir
    @time    = Time.at(Time.now.to_i - 60 * 60 * 24)
  end

  def run
    Pathname.new("#{maildir}/cur").entries.each do |path|
      file = Pathname.new("#{maildir}/cur/#{path.to_s}")
      archive(file) if file.file?
    end
  end

  def archive(file)
    mail = Mail.read(file.realpath)
    return if mail.date.to_time > time

    puts "#{mail.date.strftime("%Y/%m/%d")}\t#{file.basename}"
    file.rename("#{archive_path_for(mail)}/#{file.basename}")

  rescue
    puts $!.inspect
    puts "Couldn't archive #{file}"
  end

  def archive_path_for(mail)
    date = mail.date.strftime("%Y/%m/%d")

    dir = Pathname.new("#{maildir}/archive/#{date}")
    dir.mkpath

    return dir
  end

end

Archiver.new("#{ENV['HOME']}/.mail").run