The report for the financial quarter ending December 31 comes as lawmakers in Congress work toward fixing the agency's troubled finances.
Officials say there was continued growth in revenue from package delivery, but first class mail continues to decline.
The Postal Service has been urging Congress to end Saturday mail delivery as it copes with steep financial losses. It lost $5 billion in the last fiscal year, down from $15.9 billion in 2012.
The agency recently won approval to temporarily raise the cost of a first-class stamp from 46 to 49 cents. The higher rate began Jan. 26.