You should put this options on your /etc/amavis/conf.d/50-user file:
$sa_tag_level_deflt = -999; # add spam info headers if at, or above that level
$sa_tag2_level_deflt = 6.2; # add 'spam detected' headers at that level
$sa_kill_level_deflt = 6.9; # triggers spam evasive actions (e.g. blocks mail)
$sa_spam_subject_tag = '**Spam**';
Configure the SPAM confidence level to the ones accordingly to your needs.
If you don't want to manage your score levels, you can set the quarantine directories to undefined ones. To do this add those lines in the same file:
$clean_quarantine_to = undef; # local quarantine
$virus_quarantine_to = undef; # traditional local quarantine
$banned_quarantine_to = undef; # local quarantine
$bad_header_quarantine_to = undef; # local quarantine
$spam_quarantine_to = undef; # local quarantine
If you want to check the information or take a look at additional information here's the Quarantine block on the AMaViS website: http://www.amavis.org/amavisd-new-docs.html#quarantine
The rules are cumulative. In some cases, such as this you will have overlapping rules triggered.
Bayes 99 to 99.9 Scores 3.5
3.5 BAYES_99 BODY: Bayes spam probability is 99 to 100%
[score: 1.0000]
Bayes 99.9 to 100% triggers two rules and scores 3.7.
3.5 BAYES_99 BODY: Bayes spam probability is 99 to 100%
[score: 1.0000]
0.2 BAYES_999 BODY: Bayes spam probability is 99.9 to 100%
[score: 1.0000]
EDIT: Amavis does seem to support testing directly.
There are some hint on testing on the mailing list. This indicates something like the following.
mini_sendmail -ftest at example.com -s127.0.0.1 \
-p8888 postmaster at example.com <test.msg
It may be possible to generate a test configuration that delivers messages to a file. See the above mailing list thread.
The amavis-new documentation indicates these is some documentation in the distribution. In particular, 'test-messages/README'.
Amavis works by re-injecting mail back into your MTA. This can result in back-scatter spam.
Best Answer
Amavis should read the standard configuration of spamassassin, so you can put your custom configuration in "/etc/mail/spamassassin/local.cf" (or similar) and it should just work.