Debian docu says i should do it this way:
CHECK_RCPT_DOMAIN_DNSBLS = zen.spamhaus.org/$sender_address_domain : dnsbl.sorbs.net/$sender_address_domain
but it does not work. my dialup ip is listed on dnsbl.sorbs.net but i can telnet to the mx and leave a message. not even a 'warning' header listed or something...
I think you want to set the CHECK_RCPT_IP_DNSBL entry. Something like
CHECK_RCPT_IP_DNSBL = zen.spamhaus.org
should work. I believe zen includes the sorbs list now. The domain blocklist is for domains likeexample.com
not IP addresses.