The key pal is the new age incarnation of a pen pal. Instead of the traditional pen and paper communication key pals will use email to communicate. This usually results in a lot higher volumes of correspondence.
Computer: "You have new mail."
Nosey friend: "Hey Bob, who's Alice?"
Bob: "Don't read my email!"
Nosey Friend: "But who's Alice?"
Bob: "It's just my key pal."
Nosey friend: "haha, you're sad!"