I simplified my access lists by creating some classifications. I added the following lines to main.cf:

#       Classifications
smtpd_restriction_classes =
        reject_RFC,
        reject_auto,
        reject_auto_virus,
        reject_domain,
        reject_dynamic,
        reject_infected,
        reject_spam,
        reject_user,
        whitelist_select
reject_RFC = check_client_access regexp:/etc/postfix/class/reject_RFC
reject_auto = check_client_access regexp:/etc/postfix/class/reject_auto
reject_auto_virus = check_client_access regexp:/etc/postfix/class/reject_auto_virus
reject_domain = check_client_access regexp:/etc/postfix/class/reject_domain
reject_dynamic = check_client_access regexp:/etc/postfix/class/reject_dynamic
reject_infected = check_client_access regexp:/etc/postfix/class/reject_infected
reject_spam = check_client_access regexp:/etc/postfix/class/reject_spam
reject_user = check_client_access regexp:/etc/postfix/class/reject_user
whitelist_select = check_client_access hash:/etc/postfix/hash/whitelist-select

Then I can write a long reject message in class/reject_spam to explain why I am not accepting the message:

/./     REJECT  Your email address or domain is used or implied in SPAM and will be disgarded as unwanted. Log files may be used in criminal or civil lawsuits.

Then in my access tables I can just use reject_spam after the email adres. Like this:

friend@public.com			reject_spam
haasje@vanderkooij.org			reject_spam