The USPS recommends the following deadlines to ensure your domestic mail reaches its recipient by December 25th.
December 14 - USPS Retail ground
December 20 - First Class
December 20 - Priority Mail
December 22 - Priority Mail Express
Be sure to thank your mail carrier for delivering your mail and packages this holiday season, they have been working long tiring hours to ensure your loved ones receive their mail in a timely manner.