Jerry Geis wrote:
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 #
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This question is probably inappropriate for this list, but maybe someone
can answer it.
Let's pretend I have a network behind a firewall. And let's pretend that
the users behind that firewall are both beyond my control, and have a
non-zero population of idiots. And further, let's pretend that these
idiots have done something to land my firewall's internet IP on a blacklist.
So now lets pretend I have a different system on the internet, running
sendmail, that I would like to use to relay mail out through, for myself
and a few carefully selected non-idiot users. And lets further pretend
that this server is a secondary MX for a whole bunch of domains and so
gets pounded with spam.
OK, I set up this server so that it grants RELAY permission in
/etc/mail/access to the IP address that is on the blacklist and
everything works.
Now I see the above post and think that adding dnsbl features to this
sendmail might be a good way of reducing inbound spam.
So my question is: if my system has granted RELAY permission to a system
which is in a dnsbl used by the sendmail configuration, does the
sendmail RELAY, or does it deny the connection attempt?
Thanks for wading through this completely hypothetical situation.
:)
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