I use Exim version 4 on Debian Sarge, and I want to start using a "Real-time Black-hole List" (RBL) service. How the hell do I do that?
On Woody, with Exim version 3 it was easy. There was an option in the /etc/exim/exim.conf configuration file called rbl_domains. All I needed to do was list the DNS blackhole list servers I wanted to use:
rbl_domains = sbl-xbl.spamhaus.org/reject
Now, how does that work in Sarge? Debian-specific documentation seems to be scant, which is a shame since Debian have their own hare-brained configuration scheme for Exim. Assuming you are using the 'split config file' scheme, here is the answer:
Create a file called something like /etc/exim4/conf.d/main/01_spamblock and add this line to it:
CHECK_RCPT_IP_DNSBLS = sbl-xbl.spamhaus.org
That doesn't do quite the same as the Exim v3 line above. By default, Debian's configuration adds a X-Warning: line to the header of messages that fail this check. That's OK with me though, because I can just filter out these messages with a rule in my mail client.
If you want to simply reject spam, then you'd probably have to change warn to deny in the file conf.d/acl/30_exim4-config_check_rcpt, here:
# Check against classic DNS "black" lists (DNSBLs) which list # sender IP addresses .ifdef CHECK_RCPT_IP_DNSBLS warn 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
There's more useful anti-spam configuration advice over on koivi.com.