It was not clear whether per capita mail included business mail carried by courier services run by the people themselves.
The Department of Posts lost 4.6 billion rupees in 2011, up from 3.0 billion rupees a year earlier, with revenue dropping 27 percent to 3.2 billion rupees.
Meanwhile expenditure had increased 5.7 percent to 7.7 billion rupees.
"Hence, it is important for DOP to continue with the efforts taken to generate other sources of income and vigorously follow cost rationalization methods to transform itself to a self- financing venture," the Central Bank said.
"The initiatives taken by the DOP to provide additional revenue generating services such as banking facilities and pre-paid phone cards, International Emergency Mail Services and Western Union Money Transfer services continued in 2011."Sri Lanka has 4,742 post offices, with 4,058 run by the state and 463 post office and 156 rural agency post offices run on an agency basis by citizens.
While mail use dropped, telephone density rose to 105.1 lines per 100 persons from 100.7 a year earlier. Mobile phones rose 6.1 percent to 18.319 million and fixed lines rose 2.9 percent to 942,000.
Sri Lanka's telecom use exploded from the mid 1990s after a state monopoly was broken and competition was allowed. Enterprises owned by citizens and non-citizens invested in the sector and started to provide telecom services.