[SDPhantom]

There isn't a reliable way to send messages between non-connected realms. Greenwall operates by having all users open a guild-specific global chat channel on the server and relays/translates messages passing through back into what looks like guild messages. To get messages between non-connected realms, you have to rely on BNet whispers, which if any user performing the transcode operation logs off, the entire addon goes down. This is logistically infeasible.