[CentOS] spam control

Gents,

I have added the following to /etc/mail/sendmail.mc and rebuilt it
trying to control spam. I still get about 25 spam messages a day.
Is there something else that can help control spam?

Thanks

jerry
---------------------------
dnl #
dnl # dnsbl - DNS based Blackhole List/Black List/Rejection list
dnl # See http://www.sendmail.org/m4/features.html#dnsbl
dnl #
FEATURE(`dnsbl', `bl.spamcop.net',     `"Spam blocked see: 
http://spamcop.net/bl.shtml?"$&{client_addr}')dnl
FEATURE(`dnsbl', `relays.ordb.org',    `"Spam blocked see: 
http://ordb.org/lookup/?host="$&{client_addr}')dnl
FEATURE(`dnsbl', `cbl.abuseat.org',    `"Spam blocked see: 
http://cbl.abuseat.org/lookup.cgi?ip="$&{client_addr}')dnl
FEATURE(`dnsbl', `sbl.spamhaus.org',   `"Spam blocked see: 
http://spamhaus.org/query/bl?ip="$&{client_addr}')dnl
FEATURE(`dnsbl', `list.dsbl.org',      `"Spam blocked see: 
http://dsbl.org/listing?"$&{client_addr}')dnl
dnl #