You can't, unless the recipient's email client displays images. Most do not do this by default.<p>If the user chooses to display images, you can include a link to a 1x1 image in the email, and then monitor your server logs to see who opens it. There are plenty of software packages that do this.<p>More information here: <a href="http://stackoverflow.com/questions/973143/tracking-email-bounces-opens-clicks" rel="nofollow">http://stackoverflow.com/questions/973143/tracking-email-bou...</a>
Check out <a href="http://www.rightinbox.com" rel="nofollow">http://www.rightinbox.com</a><p>Right Inbox puts a small invisible image in your email. If the recipient’s email client does not particularly block remote images, then tracking takes place. Plus, if you include links in your email, they are also included in tracking. If the recipient clicks a link, then it is notified to you regardless of their email client or so.
1. Make it short
2. Add a link to your domain
3. Add getClicky to your domain<p>A large number of readers will click on your link. As a recipient of some of these emails, I almost always click on a company name just to get more info on the company. So, if you keep the message tight, you can usually see if they read the email because there's a hit on your website.
<a href="http://www.yesware.com/" rel="nofollow">http://www.yesware.com/</a> is free to use and also works with the 1x1 image to track opens. You can also add trackable links.