Dear Professor McGonagall,
I am sending this letter through normal postal channels, as I have no idea how to send a letter using a nonexistent bird of prey. I have no intention of giving up the normal world, simply to go to a magic school and act famous. I have a good life here, and I have no reason to throw that away for nothing. Having read the history books I got from Diagon Ally, I am forced to conclude that your magic either drives you insane, or your entire population is suffering from neural defects due to inbreeding. I have no reason to become a part of an insane world, and many reasons to avoid it like the black plague.
Sincerely,
Harry Potter