From Kolab wiki

Enabling the use flag spam

If you enable this use flag amavisd will be configured so that it uses external services for spam checking. There are three tools that the kolabd ebuild will depend on if this flag is activated:

• razor
• pyzor
• dcc

The amavis configuration file will then be set to

$sa_local_tests_only = 0; 

so that spamassassin will use the external tools.

In addition some templates for the spamassassin configuration are added to the /etc/kolab/templates directory. They will end up in the following positions:

• [source:ebuilds/net-mail/kolabd/files/local.cf.template /etc/mail/spamassassin/local.cf]
• [source:ebuilds/net-mail/kolabd/files/v310.pre.template /etc/mail/spamassassin/v310.pre]

If you wish to register with razor so that you can also report spam, you can run

mkdir -p /etc/mail/razor && chown amavis:amavis /etc/mail/razor" 
su -s /bin/bash - amavis razor-admin -home=/etc/mail/razor -register my@mail.com
su -s /bin/bash - amavis razor-admin -home=/etc/mail/razor -create

Edit /etc/mail/razor/razor-agent.conf afterwards and link to the newly created identity.