PostInstall.txt

For more information on bounce_email, see http://bounce-email.rubyforge.org

You can easily use this plugin with e.g. Rails application.
Configure rails, so it send email using postfix and it adds VERP.
#- in environment.rb file add lines -#
config.action_mailer.delivery_method = :sendmail
config.action_mailer.sendmail_settings = {
  :location       => '/usr/sbin/sendmail',
  :arguments      => '-XV -f bounces-main@amerimail.lv -i -t'
}
#- end -#
Change amerimail.lv to email server that will handle bounce emails.

Follow this tutorial to handle bounce-emails: http://keakaj.com/wisdom/2007/08/08/verp-on-rails/

You can make Ruby file like this:
require "rubygems"
require "mail"
require "bounce_email"

mail = Mail.new(STDIN.read)
bounce = BounceEmail::Mail.new(mail)

# Do something with bounce info
# bounce.isbounce -> true/false
# bounce.code -> e.g. "5.1.1"
# bounce.reason -> e.g. "Something about the address specified in the message caused this DSN."
# bounce.type -> e.g. "Permanent Failure"

# Permanent Failure means that it is hard bounce
# Persistent Transient Failure means that it is soft bounce

# If reason is "Vacation auto-reply" then email could be vacation email (but it is rearly cought).