USPS: The United Postal Services will make one or two attempts to deliver, based on the carrier’s knowledge. After the attempts, the package will be held for 15 days from the initial delivery attempt. If nobody goes for the parcel within 15 days it'll be returned to sender.
UPS: makes up to three delivery attempts, excluding weekends and holidays. The third and final delivery attempt has been made, and the driver was unable to leave your package. UPS reserves the right to return the package to the shipper after three delivery attempts.
DHL: After two attempts, the package will be held at the local DHL office until delivery arrangements are made. In most cases, the local DHL office will return the package to the sender in 7 business days, unless previous arrangements have been made.