Simple Email Blacklist Using Spamassassin Plugin And RBLDNSD

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This is not new idea, actually. someone at spamassassin plugin developers have been made before. basically, the idea was put email addresses in RBLDNSD zone dnset format, ie:

Email
user@example.com

RBLDNSD
user.example.com

So, we replace @ sign into dot (.) sign. that way, we can save the email addresses into the RBLDNSD dnset zone.

RBLDNSD part:

create emailbl zone, meta information

zone

:127.0.0.4:DNSBL. $ - Not receiving email right now.
example.user.gmail.com
example.user.rediffmail.com

meta

$NS 1w ns.example.com ns.example.com
$SOA 1w ns.example.com admin.example.com 0 2h 2h 1w 1h
$DATASET generic @
@ A 1.2.3.4
@ MX 10 mx.example.com
@ TXT "example email blocklist"

in /etc/sysconfig/rbldnsd

RBLDNSD="dsbl -r/var/lib/rbldns/dsbl -t 300 -b 1.2.3.4 \
emailbl.example.com:combined:meta,emailbl
"

ofcourse we should delegate the subdomain emailbl.example.com in example.com authoritative nameserver

; subdomain delegation
emailbl.example.com.	IN NS ns.example.com.
ns.example.com.			IN A 1.2.3.4

start rbldnsd service

service rbldnsd start

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Postfix, Rate Limiting Inbound Emails Using SenderScore And Memcache

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I received email from someone fiew days ago, he directed me to an article about senderscore and and asked if I could make it usable. Actually, I’m not very familiar with how senderscore work. I’ve read the article and see the FAQ at https://senderscore.org/. I have found that senderscore can be queried with a format like this:

reversed.ip.address.score.senderscore.com

Ie, I want to know the score value of ip address 202.127.97.97, the format of the query would be like this:

$ dig a 97.97.127.202.score.senderscore.com +short
127.0.4.75

Look at the answers given by senderscore’s NS. last octet is the score of the ip address 202.127.97.97, which scored 75.

Excerpts from senderscore faq:

All scores are based on a scale of 0 to 100, where 0 is the worst, and 100 is the best possible score. A score represents that IP address’s rank as measured against other IP addresses, much like a percentile ranking.

Now back to the article, The authors make a perl module that can perform queries to senderscore ns, put a “reputation score” into memcache, at the same time, calculating how many times an ip address connected to our smtp.

Let’s begin, first of all download Policy::Memcache from this git repository 
Create a working directory, and extract the tarball.

$ mkdir pol-mem && cd pol-mem
$ tar --extract --file=petermblair-libemail-f73612c.tar.gz petermblair-libemail-f73612c/perl/senderscore/memcache/
$ mv petermblair-libemail-f73612c/perl/senderscore/memcache/* .

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