All notices and written communications to claimant will be mailed to the last address supplied, either on the employer's first report of injury or by claimant's letter. If the board is notified that claimant is represented by an attorney, copies of forms, notices, and correspondence will thereafter be mailed to his attorney and not to the claimant. However, copies of compromise approval notices, prehearing setting, and awards of the board will be mailed to the claimant and his attorney.