require 'net/imap'

ADMIN_USER = 'blah'
ADMIN_PASS = 'blahpass'
IMAP_HOST  = 'imap.domain.org'

username = ARGV.first

Net::IMAP.debug = 10
imap = Net::IMAP.new(IMAP_HOST)

imap.authenticate('LOGIN', "#{username}*#{ADMIN_USER}", ADMIN_PASS)
imap.list("", "*").map {|m| m.name }.each do |mailbox|
  imap.select(mailbox)
  imap.expunge
end