Happy Mail how does it work?

ive connected my 2 idls a few times. The Happy Mail is the only thing that's grey and inactive. My question is, how do I get a happy mail? Cause I remember in the past when I connected both, I get a message in the "outside" of my tama's house, in the yard, as a "flying paper plane." After I finish reading the message, I press a random button, and it disappears. So is that where I was suppose to save my letters? For future happy mails?

Or how is it that youre to activate the Happy Mail function?

ok never mind, I got my answer, thanks. no need to reply.