How do I report a spam?
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 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/code/teach-sa/
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.
Setup of special aliases in Postfix to forward spams and hams
A very convenient way of reporting spam is to forward spam into a special alias. The following page shows how to configure such alias and perl script for mail attachment extraction : http://gtmp.org/pub/sa-postfix.en.html
A modified version of this script can be found here: https://po2.uni-stuttgart.de/~rusjako/sal-wrapper/
Thunderbird and Outlook plugin
This is a basic plugin, which reports a Mail as spam (or ham) from these mailreaders. Its available at http://sourceforge.net/projects/soc2006spamd/ You need a running spamd on the server side and the plugin talks spamd protocol.
Reporting spam which passed specific accreditation rules
Some rules check particular accreditation programs, or whitelists. If you feel that a message source was accredited or whitelisted inappropriately, it may be worthwhile to report the problem rather than simply discounting the rule.
Return Path is a commercial entity which operates multiple accreditation services.
Issues with messages which match RCVD_IN_BSP_TRUSTED may be reported to senderscorecertified.com at abuse.net.
DNSWL is a free accreditation service Issues with messages which match RCVD_IN_DNSWL_* may be reported to admins at dnswl.org. Please send the headers of the mail separately and attach the message.