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DNS Blacklist with Exim
Before getting started, we suggest you Learn Linux Basics and follow these precautions.
By setting the anti-spam DNS Blacklist feature in Exim you can eliminate a majority of your daily spam in a few simple steps.
This How-To is written for Debian Linux, with Exim using split configuration files. If your installation of Exim isn't utilizing split configuration, simply make all additions to your /etc/exim4/exim4.conf.template file.
Edit the file /etc/exim4/conf.d/main/02_exim4-config_options and insert the following after the very last line.
# Added TODAYS-DATE by YOUR-NAME # Spamhaus RBL zen.spamhaus.org CHECK_RCPT_IP_DNSBLS = zen.spamhaus.org
Note: By itself Spamhaus provides dependable real-time anti-spam protection, but alternatively you may choose to add more than one DNS Blacklist from another source. Just be sure to separate each entry with a colon.
Edit the file /etc/exim4/conf.d/acl/30_exim4-config_check_rcpt and search for CHECK_RCPT_IP_DNSBLS acl, then change the word "warn" to "deny" as shown below:
# Check against classic DNS "black" lists (DNSBLs) which list # sender IP addresses .ifdef CHECK_RCPT_IP_DNSBLS deny message = X-Warning: $sender_host_address is listed at $dnslist_domain ($dnslist_value: $dnslist_text) log_message = $sender_host_address is listed at $dnslist_domain ($dnslist_value: $dnslist_text) dnslists = CHECK_RCPT_IP_DNSBLS .endif
Restart Exim so that our configuration changes take effect:
Once you have set up your mail server to use zen.spamhaus.org, you can test to see if the PBL blocking is working by sending an email (any email) to: email@example.com (you must send the email from the mail server which you wish to test). The Crynwr system robot will answer you to tell you if your server is correctly blocking PBL-listed IP addresses or not.
The email will look something like this.
220 mail.linuxlookup.com ESMTP Exim 4.69 Sat, 26 Sep 2009 12:11:10 -0400 helo pbl.crynwr.com 250 mail.linuxlookup.com Hello nelson at pbl.crynwr.com [220.127.116.11] mail from:<> 250 OK rcpt to: 550-X-Warning: 18.104.22.168 is listed at zen.spamhaus.org (127.0.0.10: 550 http://www.spamhaus.org/query/bl?ip=22.214.171.124) Terminating conversation
If everything is set-up correctly, you should see "Terminating conversation".