Adding RBLs to sendmail

[Hendrik den Hartog]

Hello

Apologies for this simple request for help, but the result would
help us tweak our MailScanner/Sendmail setup.

I note advice about adding RBLs to sendmail, e.g.
from a post by Denis Beauchemin,

FEATURE(`dnsbl',`safe.dnsbl.sorbs.net',`"554 Rejected " $&{client_addr} 
" found in safe.dnsbl.sorbs.net"')dnl
FEATURE(`dnsbl',`cbl.abuseat.org',`"554 Rejected " $&{client_addr} " 
found in cbl.abuseat.org"')dnl

What I'd like to know is what is the minimum version sendmail I 
can add entries like this to?
Any advice, links, etc, appreciated...

Cheers!
Dave