Which service guarantees overnight or next day delivery with $100 insurance and free tracking?

The service that guarantees overnight or next day delivery, along with $100 insurance and free tracking, is Express Mail. This premium service is designed for urgent shipments, ensuring that customers receive their packages swiftly, typically by the next day, even on weekends and holidays in some areas.

Express Mail stands out because it not only provides speed but also includes essential features like automatic insurance coverage for items valued up to $100 and tracking capabilities at no additional charge. This makes it an ideal option for sending critical documents or packages that require quick delivery and added security.

In contrast, other services like Priority Mail, while fast, do not come with the same guaranteed overnight delivery promise and specifics related to insurance and tracking. Parcel Select is typically a more economical option for shipping large volumes but does not offer these guarantees. Standard Mail is primarily used for bulk mailing and does not focus on speed or insurance, as it is intended for less time-sensitive items.