Banned files are being quarantined, spam isn't

[Benedict White]

I have a new Amavisd install with SQL for both lookups and storage dsn's.

When I send a banned file through to a user with a policy that blocks it,
It ends up in quarantine which what I would like. I can then release the mail OK

However, when I generate a really spammy email (score over 28) it 
Goes through, though it seems to generate a quarantined item in MailZu 
Though releasing it doesn't do anything as presumably the mail isn't there.

I have the following set for the policy row in the policy sql table:
spam_tag_level  1 
spam_tag2_level 6.31 
spam_tag3_level 8
spam_kill_level 10 
spam_dsn_cutoff_level 12 
spam_quarantine_cutoff_level 20

What do I need to do to get seriously spammy emails into quarantine?

Kindest regards,

Benedict White