There are probably not very many of your friends who read this forum, if any at all.
Only a very small % of players use this forum. And the few players who use this forum come from ALL of the worlds on the EN server; not only from "your world".
Use the in-game Message Center to make sure your friends receive your messages.
You'll have to add your friends one by one to a message though. It's not possible to add all friends at once.