You could ask for a read receipt with Outlook or Thunderbird. However, you won't get any receipts, if the receiver's client doesn't support it.
Tracking newsletters is working by clicking on links or loading of images. You could set up a signature for your mail that contains an image hosted on a remote server. Simply read out the log files afterwards or use dedicated analytics scripts like Piwik. Once more, this won't work, if the receiver doesn't load images or prevents access to your remote server by some firewall.
I guess, your success with tracking mail will principally depend on user habits and won't be some reliable measure to proof message reading.