Maybe, but it's not a sure thing.
One thing you can do is put a "Read Receipt Request" on the email. Many email clients will then mail a read-receipt back to the sender, although this depends on the mail client and whether the recipient allows it.
The second thing you could do is incorporate an image-tracking "bug" into the mail. If you are sending an HTML mail, you can incorporate an image URL with a unique key into the email. The "image" would be a PHP script that tracks the unique key, then serves the image. The downside to this is that it's a known spammer tactic for finding "live" addresses, and most email clients do not show hotlinked images by default. If your content was compelling enough and required the images, you might be able to get people to "click through" and allow the images, but it's still not a sure tracking method.
On the same note, you could make the message a "teaser", and link the recipient to the body of content, displayed on the Web, adding a tracking key into the URL.
There is, however, no completely reliable way to track whether any given message has been read.
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