Remove your oil painting from its frame carefully.
Place thin plastic sheeting on both sides of your painting and roll it around a cardboard tube, with the painted side on the inside.
Place bubble wrap around your picture and secure with a rubber band at each end of your tube.
Slide your oil painting into a specialist mailing tube, and seal it according to the manufacturer's instructions.
Affix an address label to your tube including the recipient's address and your return address.
Take your packaged painting to your local post office, and send it via the U.S. Postal Service's special handling service. Tell the postal worker handling your request that the contents are fragile. Discuss insurance options if your painting is valuable.