forward.rb

#!/usr/bin/env ruby
# coding: utf-8

require 'net/pop'
require 'net/smtp'

AUTH = {
  from: '', to: %w[],
  pop:  {host: '', ssl: true, user: '', pass: ''},
  smtp: {host: '', port: 587, user: '', pass: ''}, 
}

_smtp = Net::SMTP.new AUTH[:smtp][:host], AUTH[:smtp][:port]
_smtp.enable_ssl if AUTH[:smtp][:port] == Net::SMTP.default_ssl_port
_smtp.enable_starttls if AUTH[:smtp][:port] == Net::SMTP.default_submission_port

_smtp.start(`hostname`.strip, AUTH[:smtp][:user], AUTH[:smtp][:pass]) do |smtp|
  _pop = Net::POP3.new AUTH[:pop][:host]
  _pop.enable_ssl if AUTH[:pop][:ssl]
  _pop.start(AUTH[:pop][:user], AUTH[:pop][:pass]) do |pop|
    pop.each do |m|
      begin 
        smtp.open_message_stream(AUTH[:from], AUTH[:to]){|f| m.pop{|c| f << c} }
        m.delete
      rescue => e
        puts e # send failed
      end
    end
  end
end