Apparently, Neilsen has disabled reply-all for all their Outhouse users, to “eliminate bureaucracy and inefficiency”.
What an incredibly stupid idea. Removing a very useful feature, just because a few people use it incorrectly? Stupid, stupid, stupid.
If people were CC’d on a mail you receive, then that mail was relevant to them, and contained info they needed. There’s a good chance your reply will also be something they should read; if that’s the case, you hit Reply All. If your reply is only relevant to the original author, just hit Reply. Really not that hard, is it?