If you use gmail or google mail, there is a solution for your curious mind! If you are not sure if your emails are getting read, check out Yesware, which lets you know when your emails have been read and even if they get forwarded by the person that received your email.
The basic version of this app is free. There are advanced versions as well, which start at $5/month (as of 9/2013).
Check out this interesting little app at yesware.com.