[1] Most tracking technologies use some form of digitally time-stamped record to reveal the exact time and date when an email is received or opened, as well as the IP address of the recipient.
However, due to the nature of the technology, email tracking cannot be considered an absolutely accurate indicator that a message was opened or read by the recipient.
Most email marketing software provides tracking features, sometimes in aggregate (e.g., click-through rate), and sometimes on an individual basis.
Some email applications, such as Microsoft Office Outlook and Mozilla Thunderbird, employ a read-receipt tracking mechanism.
Depending on the recipient's mail client and settings, they may be forced to click a notification button before they can move on with their work.
Read receipts are sent back to the sender's "inbox" as email messages, but the location may be changed depending on the software used and its configuration.
The technical term for these is "MDN - Message Disposition Notifications",[2] and they are requested by inserting one or more of the following lines into the email headers: "X-Confirm-Reading-To:"; "Disposition-Notification-To:"; or "Return-Receipt-To:".
These response events accumulate over time in a database, enabling the email marketing software to report metrics such as open-rate and click-through rate.