Can Hotmail confirm that the schools server received the email

My son is epileptic and has been bullied by a teacher at school.  I emailed a formal complaint letter which the school have told me they never received.  It was in my sent folder, it did not bounce back, I did not receive any failure notifications.  I am sure the school have deleted the emails as they did not want to deal with the issue in writing.  I need to prove that the email was received by their server.  Please can someone help me.