WiiConnect24 has been discontinued - this is true.
That DOES NOT MEAN you cannot send letters to other people. You just have to *cough* do some stuff that this forum does not allow me to discuss HOW to do.
It's called RiiConnect24 (Get it? RE-Connect?!) and if you're willing to do what is necessary then it will work again. RiiConnect24 is a third-party created service to replace what was once WiiConnect24. It works - I know, because I did it to MY Wii and everything works, even the News Channel, Weather Channel, Everybody Votes Channel, etc. All of that works again. And because I also use Wiimmfi on my Wii, I can also visit other people in City Folk and they can come visit me.
Again, I can't tell you HOW to do it because of forum rules. I can only tell you that you CAN do it - and that Google is your friend in this.
No problems. It would have been more helpful if the forum admins would allow me to link specific sites with guides on how to do both RiiConnect24 and Wiimmfi because then people with City Folk would be able to follow a tested and proven guide to play with other people if they want. It also allows people to play Mario Kart Wii on-line. And, in fact, there's a sizeable player base for MKWii - it's the biggest game on Wiimmfi by a huge margin. Every day there are hundreds of people playing that game together - averaging around 300. I've seen as high as 500 before.