centos-bounces@centos.org <> scribbled on Wednesday, October 25, 2006 3:51 PM:
David Mackintosh spake the following on 10/25/2006 10:54 AM:
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?%22$&%7Bclient_addr%7D%27)dnl FEATURE(`dnsbl', `relays.ordb.org', `"Spam blocked see: http://ordb.org/lookup/?host=%22$&%7Bclient_addr%7D%27)dnl FEATURE(`dnsbl', `cbl.abuseat.org', `"Spam blocked see: http://cbl.abuseat.org/lookup.cgi?ip=%22$&%7Bclient_addr%7D%27)dnl FEATURE(`dnsbl', `sbl.spamhaus.org', `"Spam blocked see: http://spamhaus.org/query/bl?ip=%22$&%7Bclient_addr%7D%27)dnl FEATURE(`dnsbl', `list.dsbl.org', `"Spam blocked see: http://dsbl.org/listing?%22$&%7Bclient_addr%7D%27)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.
:)
If you allow in the access file, it should override the dns blacklist. So if you allowed an address in the blacklist, it should let it through.
I think this is true IF you have FEATURE(delay_checks) specified in your sendmail.mc (thus your cf)
Mike