It said pre-tax profits for the year to the end of March were £267m compared with £400m a year earlier.
Royal Mail chief executive Moya Greene said: "We have delivered a resilient performance in challenging markets."
UK revenue fell 1% to £7.6bn from £7.7bn a year earlier as letter volumes and revenue fell by 3% and 2%.
UK parcel volumes grew 3%, but revenue was only 1% higher.
Parcel volumes at Royal Mail's European division, GLS, grew 10% while revenues were up 9%.
That helped total group revenue rise 1% to £9.2bn in the year.
The company's preferred measure of profit - adjusted annual operating profits before transformation costs - rose 5% to £742m from £740m a year earlier.
Transformation costs included 3,500 voluntary redundancies, which cost the business £117m in the year. Overall transformation costs rose to £191m in the year.
Royal Mail said it reduced costs at its UK parcels division by 1%, while net debt fell to £224m.
It added the fall in annual pre-tax profits was the result of last year's results being boosted by the profit on the sale of its Paddington depot in west London.
Royal Mail has reported a 33% fall in annual profits and warned that market conditions remain "challenging" despite rising parcel volumes.