Many mailers turned to Priority Mail Express 1-day shipping this holiday season.
Employees may remind customers that they will not qualify for refunds if USPS attempted to deliver any Priority Mail Express 1-day package mailed between Dec. 22, and Dec. 25, 2015, within two business days.
USPS competitors use similar refund policies during the holidays. More information on the Priority Mail Express holiday refund policy is available to customers by visiting the Domestic Mail Manual.
Source: Refund reminder | USPS News Link