Most Helpful Guy
That rather depends on the letter, on his general personality, and how the relationship ended.
I would recomend not expecting anything back though, as you say you didn't even intend to send what you did.
Most Helpful Girl
haha been there done that.
From my experience he won't respond.
Don't worry I know how you feel I've done this before (maybe more than once). They never respond.
Going forward do your best to keep your feelings to yourself to save yourself from humiliation. I always thought "I don't care what he thinks" but honestly it's better they don't know. Whether they know or not doesn't make a difference, at least make them think yuo're doing better than they hope.