Return table with separate columns from function
To get decomposed, separate columns, call the table function with:

SELECT * FROM test_function();


But you also have sneaky naming conflicts. The column names listed in the RETURNS TABLE clause are implicit OUT parameters, visible in every SQL statement in the function body. Avoid using names that conflict with column names and/or table-qualify all possibly conflicting table column names in the function body. Like:

CREATE OR REPLACE FUNCTION test_function()
  RETURNS TABLE (id int, organization_id int, email_address varchar) AS
$func$
SELECT u.id, u.organization_id, u.email_address FROM users u;
$func$ LANGUAGE SQL;

See: Variable Substitution in the manual.