The federal government will shut down tomorrow (Wednesday) per orders from Trump. Because of that, there will be no USPS mail delivery service aside from some packages.
USPS said, “Out of respect for the 41st President of the United States and to honor his vast contributions to our country during his lifetime, and consistent with the Presidential Proclamation, the United States Postal Service will suspend regular mail deliveries, retail services and administrative office activity on Dec. 5.”
They added that limited package service will be in effect because of the holidays. This is to maintain the flow of service and to help avoid a backup since it’s the busy time of year for packages.