In order to test how many people open an email, you need to send it in HTML format and include a 1x1 invisible image for tracking the open rate.  
This can be done e.g. with the Add2it Go-To System.

Please check out the video / PDF tutorial at:  http://GoTo-Pro.com/video-email.php

BTW... There is no reliable way to check on the delivery rates of your emails as some ISP's like e.g. Hotmail don't send bounce messages back to the sender.