I have discovered what appears to be a bug in the way that Exchange handles rejection of messages by a remote server. Consider this scenario:- I send a message from an Exchange server to a remote site that implements greylisting, and my message contains a virus.- The remote server at first temporarily rejects the message with something like this:451 You have been greylisted - try again in 5 minutes- Exchange duly tries again, only to be permanently rejected something like this:550 Go away, viruses are not welcome hereNow Exchange sends me a message saying that my message could not be delivered, but erroneously states the cause as451 You have been greylisted...Surely Exchange should report the last/most severe error, not the temporary rejection resulting from greylisting?Is there a more formal place to report this?Richard