Greylisting

There are different tools for greylisting.

Postgrey

Postgrey is greylisting software for the postfix MTA.

How to get it

Download postgrey from http://postgrey.schweikert.ch/

How to set it up

• Extract your postgrey package, e.g.:

tar xvzf postgrey-1.32.tar.gz

• install some needed packages

yast -i perl-BerkeleyDB

• Copy postgrey_whitelist_clients to /etc/postfix/
• Copy postgrey_whitelist_recipients to /etc/postfix/
• Add a user named postgrey:

useradd -m postgrey

• Add a directory for the lock file:

mkdir /var/spool/postfix/postgrey
chmod 777 /var/spool/postfix/postgrey

• start postgrey

./postgrey --inet 127.0.0.1:60000

If you get an error, see TroubleShooting.

• make sure postgrey is listening on port 60000:

$ nmap localhost -p59998-60002

Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2007-08-10 07:44 CEST
Interesting ports on lvps87-230-12-146.dedicated.hosteurope.de (127.0.0.1):
PORT      STATE  SERVICE
59998/tcp closed unknown
59999/tcp closed unknown
60000/tcp open   unknown
60001/tcp closed unknown
60002/tcp closed unknown

Nmap finished: 1 IP address (1 host up) scanned in 0.049 seconds

• Make sure there is a line like this in /etc/postfix/main.cf:

smtpd_recipient_restrictions = permit_mynetworks,
                                permit_sasl_authenticated,
                                reject_unauth_destination,
                                check_policy_service  inet:127.0.0.1:60000

• restart postfix

/etc/init.d/postfix restart

TroubleShooting

Symptome: When starting postgrey, you get an error message

Can't locate Net/Server.pm in @INC 

Reason: Your perl is installed, but missing Net::Server

Solution: Install Net::Server via cpan:

perl -mCPAN -e CPAN::Shell

If you have never run CPAN before, you have to answer 25 questions now. Then issue:

install Net::Server

See also

http://www.debuntu.org/postfix-and-postgrey-a-proactive-approach-to-spam-filtering