Mail tracking is a service that allows senders and recipients to monitor the status and location of a package or letter as it moves through the postal system. By using a unique tracking number, individuals can check online or through an app to see when their mail is sent, in transit, and delivered. This service is commonly offered by postal services and courier companies, such as USPS, FedEx, and UPS. Mail tracking provides peace of mind, ensuring that important items arrive safely and on time, while also allowing users to plan for their delivery.