Tired to delete bounced email generated by Comment Notifier (and Newsletter) I wrote today a bounce detection plugin. It’s very simple and need a specific mailbox to be scanned to look for bounced email addresses.
I named it, with the classical coder fantasy, Bounce.
So, if you can setup a POP3 mailbox and your provider let you to change the return path of sent email (there is an option on Bounce administration panel), you can give it a try. The Bounce official page explains how it work and how to configure it.
It does not break your blog and can be really useful if you have Newsletter plugin or Comment Notifier plugin installed.