With Mailster you get many details from your subscribers: clicks opens, unsubscriptions, and bounces. If you watch your website’s visitors via an analytics system like Google Analytics or Piwik you can now track your newsletter campaigns with them too.
I’ve released two free add-ons on the WordPress repository which are easy to set up.
Google Analytics Extension
after activation you can access a new tab on the settings page:
You can define the parameters for each campaign separately