The idea was to have two OpenBSD machines with pf + spamd to serve as mail
firewall. After that we get postfix + spamassassin + clamav + clamsmtp. Here,
postfix reads an hash database generated by postmap to see if the email address
is valid. And yes, only the full email address + domain is put in this hash db
and nothing else. These are all virtual users, so we don't use any local
accounts or whatsoever. After all the checking, we want to use maildrop as
filtering language. Here, we want to quarantine spam mails that are tagged by
spamassassin to a seperate folder. Also we want to use relaydb to forward the
spam email to the mail firewalls (where after spamassassin tagged an X amount of
messages as spam from 1 MTA, the sending MTA will be blocked.)