I see that, to report SPAM and have spamassassin "learn", I can do "spamassassin -r < message.txt".
However, it is not clear what form "message.txt" should take. Since, by the time my mail client receives the missed SPAM, it has been altered from its "native" internet email form, I will have to save it as text and submit it. I can rather handily view the "message source" which includes the "mail hop" info as well as the message body. (aka Mime.822 ?). I suspect that would be Too Much Information. Guidance?