Rails bin script to listen for emails delivered to filesystem and open with Mail (on a Mac)

mails

#!/usr/bin/env ruby
require 'listen'

APP_ROOT = File.expand_path('..', __dir__)

listener = Listen.to("#{APP_ROOT}/tmp/mails") do |_modified, added, _removed|
  added.each do |added_file|
    if added_file.end_with?(".eml")
      system("open -a Mail #{added_file}")
    else
      File.rename(added_file, "#{added_file}-#{Time.now.to_i}.eml")
    end
  end
end

listener.start
sleep

ActionMailer relies on the mail gem to deliver emails to the filesystem, and mail's FileDelivery#deliver! method names those files the destination email address. So this script first renames the file appending a timestamp and .eml extension, then opens the renamed file.