file main.cf:
smtpd_restriction_classes =
   greylist


smtpd_recipient_restrictions =
    ...
    check_sender_access pcre:/usr/local/etc/postfix/greylist.pcre
    check_helo_access pcre:/usr/local/etc/postfix/greylist.pcre
    check_client_access pcre:/usr/local/etc/postfix/greylist.pcre


file /usr/local/etc/postfix/greylist.pcre:
/post[fm]/ dunno
/sourceforge/ dunno
/(\.fr|\.th|\.id|\.jp|\.kr|\.br|\.it|\.dk|\.be|\.pt|\.ru|\.hu|\.es|\.info|\.pl)$/ greylist
/(broad|optonl|dyn|ppp|dial|cable|dsl|spark|volksbank|charter|rr.com)/ greylist
/\d+[-.]\d+[-.]\d+.*[A-Za-z]+/ greylist
/\-[a-z0-9]+\-.*\.[a-z0-9]+/ greylist
/\'/ greylist
/@[0-9]/ greylist
/t\-online/ dunno
/gmx/ dunno
/leaseplan/ dunno
/siemens/ dunno
/ford/ dunno
/[^@].*\d$/ dunno
/[bcdfghjklmnpqrtvwxyz]{4,}.*\@/ greylist
/[aeiou]{4,}.*\@/ greylist
/\d[-.]\d[-.]\d/ greylist