RE: Any rule to flag missing message-id's as SPAM?

[Rosenbaum, Larry M.]

> Hmmm....  Perhaps the protocol could had a mechanism added so that the
> server could tell if it is talking to a peer (another MTA) or a client
> (an MUA).

There is such a mechanism in RFC-2476, but I don't know how many MUAs
and MTAs support it.