the nuclear option

#!/usr/bin/ruby 


require 'net/imap'
require 'date'
require 'rubygems'
require 'active_support/core_ext/array/grouping'

include ActiveSupport::CoreExtensions::Array::Grouping

mailbox = "Inbox/Cron"
host = ''
port = 143

username = ''
password = ''

conn = Net::IMAP.new(host, port)
conn.login(username, password)
conn.select(mailbox)

date = (Date.today - 10).strftime("%e-%b-%Y")
msg_ids = conn.search(["SUBJECT", "Cron", "SINCE", date ])
msg_ids.reverse!

puts "Found #{msg_ids.length} messages in #{mailbox} since #{date}"
puts "First subject line: #{conn.fetch(msg_ids.first, "BODY[HEADER.FIELDS (SUBJECT)]")}"

flags = [:Seen, :Deleted]

msg_ids.in_groups_of(200) do |msg_group|
  conn.store(msg_group.compact, "+FLAGS", flags)
  conn.expunge 
end

conn.expunge
conn.logout