Setting up rblsmtpd

NB: you can skip this page if you decided to use qmail-dnsbl instead

 

• Info: https://www.fehcom.de/ipnet/ucspi-tcp6/man/rblsmtpd.1.html
• Greetdelay patch by Erwin Hoffmann: http://www.fehcom.de/qmail/qmail.html##greetdelay

A Realtime Block List (RBL) is a list of addresses that an RBL list supplier believes are a source of Spam.
rblsmtpd blocks mail from RBL-listed sites. It works with any SMTP server that can run under tcpserver.

qmail-smtpd's run script is already set to run rblsmtpd before qmail-smtpd. The following lines are related to rblsmtpd (others are omitted):

# This enables greetdelay anti-spam functionality on rblsmtpd
export GREETDELAY=15

# This disables rblsmtpd reject
#export RBLSMTPD=""

exec /usr/local/bin/softlimit -m "$SOFTLIMIT" \
    /usr/local/bin/tcpserver -v -H -R -l 0 \
    -x /home/vpopmail/etc/tcp.smtp.cdb -c "$MAXSMTPD" \
    -u "$QMAILDUID" -g "$NOFILESGID" 0 25 \
    /usr/local/bin/rblsmtpd -W \
        -b -r zen.spamhaus.org \
        -b -r bl.spamcop.org \
    /var/qmail/bin/qmail-smtpd 2>&1

Since rblsmtpd is the first program who talks with the sender you may want to enable the GREETDELAY here and not inside qmail-smtpd. GREETDELAY=15 sets a delay of 15 seconds. In this example two different RBL sources will be queried. If their responce is ok the qmail-smtpd program will be run.

To disable rblsmtpd you have to delete the following lines from the code above:

/usr/local/bin/rblsmtpd -W \
        -b -r zen.spamhaus.org \
        -b -r bl.spamcop.org \

NB: If you decide to use zen.spamhaus.org as suggested here, check the free use terms and be aware that exceeding these terms causes the cut off of your server. I think that one of my servers has been banned, since I can't resolve  zen.spamhaus.org.

Testing spamhaus.org

Connect to Russel Nelson's http://www.crynwr.com/spam/ site and follow the instructions. In a few words you have to do a telnet ns1.crynwr.com from your mail server and look if spamhaus.org is working fine as a filter.

Howto avoid being "cut off" by spamhaus.org

You may be interested at this point to take a look to the idea of Costel Balta, which is addressed to decrease the amount of connections to the RBL lists, avoiding to be banned consequently.