There’s a field that limits the number of days a post can be replied to via email, the default being 90 days.
If a reply is attempted after that, it appears that it gets logged as a ‘‘ReplyUserNotMatching’’ error and the user is notified that the post was not accepted, but not the real reason why.
That confuses users; it would be better if the message said something about the message to which a reply was attempted was too old. (I know, the limit can be overridden.)