The U.S. attorney's office did not immediately have the relationship between the pair.
Prosecutors say the two pleaded guilty to conspiracy to use unauthorized access devices and use of unauthorized access devices.
The Gregorys used postal service credit cards to buy gasoline for themselves, plus sell it to people in Texas, Arkansas and Louisiana. They have paid restitution of more than $47,000.
Paul Gregory is a former postal contractor. Millie Gregory used to work for the federal agency.
Simms is 150 miles northeast of Dallas.
