Email tracking is a method for monitoring whether the email messages is read by the intended recipient. Most tracking technologies use some form of digitally time-stamped record to reveal the exact time and date that an email was received or opened, as well as the IP address of the recipient. Email tracking is useful for when the sender wants to know whether the intended recipient actually received the email or clicked the links. 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. Read-receipts Some email applications, such as Microsoft Office Outlook and Mozilla Thunderbird, employ a read-receipt tracking mechanism. The sender selects the receipt request option prior to sending the message, and then upon sending, each recipient has the option of notifying the sender that the message was received or read by the recipient. However, requesting a receipt does not guarantee that one will be received, for several reasons. Not all email applications or services support sending read receipts, and users can usually disable the functionality if they so wish. Those that do support it are not necessarily compatible with or capable of recognizing requests from a different email service or application. Generally, read receipts are only useful within an organization where all mail users are using the same email service and application. 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. Even though it is an opt-in process, a recipient might consider it inconvenient, discourteous, or invasive. 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. Additional technical information, such as who it is from, the email software they use, the IP addresses of the sender, and their email server is commonly available inside the headers of the read receipt. The technical term for these is "MDN - Message Disposition Notifications", 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:". Several email tracking services also feature real-time notifications, producing an on-screen pop-up whenever the sender's email has