luceos Yes, that's true. Anyway it works for my needs (message get to who they should) EXCEPT that it seems if I send a message to two users, an email does not always come to both users notifying them. It seems more consistent when I am replying to another user in a topic. Not sure if there is some error on my part. Probably not a problem with byōbu I guess.
EDIT
I think the problem is my misunderstanding of Flarum. I am learning both the platform and THIS extension at the same time and getting confused.
1) In a normal topic (sent to a tagged topic), the first message doesn't seem to notify anyone. Or so it is for me...this would seem to be a problem since other members do not know there is a new message or topic).
2) Likewise, in a message using byōbu. (Unless I add @user).
3) But in both cases a REPLY will send a notification mail.
(In a private message, I seem to need to add @user, or REPLY to the first message)
Now I wonder if I still fail to understand something....