For what it's worth, I just tested the following code and it works for me:
using (var conn = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\__tmp\testData.accdb;"))
{
conn.Open();
using (var cmd = new OleDbCommand(
"UPDATE Ontwikkeldossier SET [In mail]=? WHERE OntwikkeldossierID=?",
conn))
{
cmd.Parameters.AddWithValue("?", false);
cmd.Parameters.AddWithValue("?", 1);
cmd.ExecuteNonQuery();
}
conn.Close();
}