Shal,
this probably is a stupid question for all IT-versed people like you. But I still pose it. If some one has a yahoo address created the way you describe in your message, and this person is - by transfer - now member of one of the groups.io, and if this person stays logged in over months in the new group and opens messages or files within the group in order to read them, without posting anything. Does yahoo then recognize this person as active with their address and spares him or her from bouncing?
Victoria
Victoria