download_email.rb

#!/usr/bin/ruby
require 'net/imap'

imap = Net::IMAP.new('imap.gmail.com', 993, true)
imap.login('[email protected]', 'wouldntyouliketoknow')
imap.select('Inbox')
# All msgs in a folder
msgs = imap.search(["SUBJECT", "Motion"])

# Read each message
msgs.each do |msgID|
  puts "Processing Message: #{msgID}"
  msg = imap.fetch(msgID, ["ENVELOPE","UID","BODY"] )[0]
    body = msg.attr["BODY"]
    i = 0 
    while body.parts[i] != nil 
      # additional attachments attributes
      cType = body.parts[i].media_type
      cName = body.parts[i].param['NAME']
      i+=1
      # fetch attachment.
      attachment = imap.fetch(msgID, "BODY[#{i}]")[0].attr["BODY[#{i}]"]
      # Save message, BASE64 decoded
      puts "Saving attachement: #{cName}"
      File.new("#{msgID}_#{cName}",'wb+').write(attachment.unpack('m'))
    end 
end
imap.close