How do I report a spam?
SpamAssassin can directly report your spam to the three HashSharingSystem it supports: see UsingRazor, UsingPyzor, and UsingDcc for details on them. To report a message, enter:
spamassassin -r < message.txt
Any SpamAssassin markup will automatically be removed (i.e., the -d option is implicitly on).
The message will also be submitted to SpamAssassin's learning systems; currently this is the internal Bayesian statistical-filtering system (BayesInSpamAssassin). Note that if you only want to perform statistical learning, and do not want to report mail to a third-party server, you should use the [http://spamassassin.apache.org/doc/sa-learn.html sa-learn] command directly instead.
Reporting spam from a maildir
This is what I use to feed mail back to spamassassin from folders on my IMAP account : http://www.ruwenzori.net/teach-sa/teach-sa.html
It works on the server side, taking input from the maildirs that provide the back-end for the IMAP server. It reads mail in designated maildir folders (spam on the one hand, ham on the other) and feeds them to spamassassin for bayesian learning and submission to various spam detection schemes while reducing training-related admin workload to nearly zero. Fits any setup storing mail as maildir, but could trivially be modified to work with mbox based systems. It depends on archivemail and formail, both packages being available from Debian.