By rule they never release the information unless they confirm it is the applicant who is mailing. Wrong info will land them in trouble. I have no issues accepting it as long as it is authentic! Also you mentioned when they know what date u applied they will say if it is thru or not. Take a scenario where the application till Oct 22nd were 7950 and on 23rd they accepted 50 out of 200 aplications to reach the 8000 quota. Now if I mail them saying my application reached on 23rd what will they say? Immigration departments dont go by what u say/ask they go my facts and only if they have verified ur application they would respond.