The U.S. Weather Service estimates the community received between 8 and 8 1/2 inches of rain.
United States Postal Service spokesman Sam Nolen says that customers will have to pick up their mail in Kenedy — 15 miles north — until further notice.
The fate of the Pettus facility depends on an environmental survey of the leased facility.
The survey results are expected sometime next week.
The USPS then will decide whether to repair the facility or to close it.