Ruby script to pull all "From:" addresses from every message in your "All Mail" Gmail folder

gistfile1.rb

#!/usr/bin/env ruby

require 'net/imap'

imap = Net::IMAP.new('imap.gmail.com',993,true)
imap.login('USERNAME', 'PASSWORD')
imap.select('[Gmail]/All Mail')
imap.search(['ALL']).each do |message_id|
  msg = imap.fetch(message_id,'ENVELOPE')[0].attr['ENVELOPE']
  from = msg.from[0]
  if from.name
    puts "'#{from.name}' <#{from.mailbox}@#{from.host}>"
  else
    puts "#{from.mailbox}@#{from.host}"
  end
end