The United States Postal Service announced in early January that it delivered approximately 524 million packages in December, an 18 percent increase over the previous year.

The volume exceeded the agency’s own predictions of a record-breaking holiday package business.

“The volume this holiday season demonstrates that retailers and consumers are turning to the Postal Service to deliver their packages,” said Postmaster General Patrick Donahoe in a Jan. 6 news release.

“We know how much our customers count on us to make sure cards, letters and gifts made it home, and I’m proud we delivered on our promise.”

The Postal Service had mounted an aggressive ad campaign to sell its Priority Mail parcel service during the holidays.

It also contracted with Amazon.com to deliver parcels for the giant retailer on Sundays during the holiday period. More than 5 million packages were delivered on the five Sundays prior to Christmas, and an additional 118,000 were delivered on Christmas Day, the Postal Service said.

It said the volume had spilled over into January because customers were opting for the Postal Service to return parcels to retailers.