You set the permissions to reviewer, did you check off anything under “write”, like “edit own” or “edit all”? If you have, uncheck them. Another question, when you “logged into” the meetingroom, do you mean you opened that room in its own outlook profile? Or did you open it on YOUR folder list and then clicked that mailbox. If you did the latter, that only sets the permissions on YOUR profile. Open the meetingroom as its own profile.