Ok,
mail-abuse.org dropped free zone transfers, then they dropped free
lookups. I am in the process of building my own black hole list for my
sendmail/bind configuration.
First I used a zone file

zone "rbl.net.home" {
        type master;
        file "rbl.zone";
};

Then,
 /var/named/rbl.zone:

$TTL
$INCLUDE ./rbl

        IN      127.0.0.2

/var/named/rbl:

$ORIGIN 0.87.165.in-addr.arpa
$GENERATE 1-255 $ CNAME $.0
63.105.29.164

Finally, this line in the sendmail configuration files
/usr/share/sendmail-cf/feature/dnsbl.m4:

define(`_DNSBL_SRV_', `ifelse(len(X`'_ARG_),`1',`rbl.net.home',_ARG_)')dnl

Run m4 /etc/mail/sendmail.mc > /etc/sendmail.cf

Restart named, restart sendmail.

A test mail sent to pat@127.0.0.2 should have bounced ( I think) due to
spam filtering... The logs look fine, host didn't resolve was the bounce.

Any ideas?

Patrick