I'm sending commercial bulk html emails to public sector addresses (ie not private individuals). I'm using SerialMailer to send them out -- basic but very easy to use.
Would like to know if there is any way to track the emails. In particular, I'd like to know the open rate.
I suggest that you may use Google analytics for that. Its free of charge and you can easily embed it in to your site. This will track any sort of web pages that are open and time spent on web page and so on.