I received an email this week asking how phpList was able to track when some one opened an email. I thought it was a good question to cover the answer here.
When we use mail list software like phpList, ListWire, Aweber, MailChimp or others, there is a ‘tracking’ feature. This tracking is different than your office email’s Read Receipt. Read Receipts are little email like messages that are sent from your readers computer back to your email. It works in a office, but not so well out on the internet.
The tracking feature of most mail list systems use a small html image embedded in the email message. When your subscriber reads the email, their email software does a html request back to the mail list server to display the small graphic image. Usually this image is a small 1 pixel white square that the reader will not notice. The html code in your email message has codes that let the mail list server know what message it came from. the mail list server then records the message as read.
The html graphic works very well, but now may email clients block images for your emails. You have probably seen the message asking you to load graphics on emails before. When you answer no or don’t load images, the mail list software will not be able to mark the message as read.
For more information and examples, check out this YouTube video on How eMail Tracking Works.