Improving Anti-spam system
We have started working with zimbra spamassasin in order to improve it. This is what we have done:
First of all, zimbra spamassassin has no SPF enabled. Since perl enviroment is system way integrated, adding SPF support is fair simple. If you use RedHat or CentOS, you can "yum-it" from dag.wieers.com repositories by executing:
yum install perl-Mail-SPF-Query
Second, we added Razor2 in order to improve score.
As root: Get razor-agents-sdk from razor.sourceforge.net, untar it and
perl Makefile.PL make make install
Get also razor-agents from razor.sourceforge.net, untar it and
perl Makefile.PL make make install
Open your firewall ports for razor2 (TCP/2703 outgoing).
Create .razor folder in /opt/zimbra/amavisd and give zimbra user permissions
mkdir /opt/zimbra/amavisd/.razor; chown -Rf zimbra:zimbra /opt/zimbra/amavisd/.razor
As zimbra user, create your razor account:
razor-admin -home=/opt/zimbra/amavisd/.razor -create razor-admin -home=/opt/zimbra/amavisd/.razor -discover razor-admin -home=/opt/zimbra/amavisd/.razor -register
And finally enable razor. Edit /opt/zimbra/conf/spamassassin/v310.pre and uncomment line
Now we are going to add pyzor support for increase (again) spam score
As root, install python support.
yum install python
Get pyzor package from pyzor.sourceforge.net, untar it and:
python setup.py build python setup.py install
Set perms according with pyzor readme.
chmod -R a+rX /usr/share/doc/pyzor /usr/lib/python2.3/site-packages/pyzor /usr/bin/pyzor /usr/bin/pyzord
As root, install pyzor RPM. It's included in the extra Repository of Fedora.
yum install pyzor . . Downloading Packages: (1/1): pyzor-0.4.0-10.fc5 100% |=========================| 65 kB 00:01 Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Installing: pyzor ######################### [1/1] Installed: pyzor.noarch 0:0.4.0-10.fc5 Complete!
Create .pyzor folder into zimbra-amavisd home and set perms
mkdir /opt/zimbra/amavisd/.pyzor; chown zimbra:zimbra /opt/zimbra/amavisd/.pyzor
Open your firewall ports for pyzor (UDP/24441 outgoing)
And ready to go, as zimbra user, with:
pyzor --homedir /opt/zimbra/amavisd/.pyzor discover
Now we have PYZOR + RAZOR + SPF. But it would be advisable to enable it and give SPF a higher score. Those admins with wrong SPF entries should be punished since it's not mandatory and so, if you enable it, do it well. So open your spamassassin config at /opt/zimbra/conf/spamassassin/local.cf and add this rules at the end (customize it at your own):
ok_languages en es ok_locales en es trusted_networks 127. 10.70. 192.168. use_bayes 1 skip_rbl_checks 0 use_razor2 1 #use_dcc 1 <<< WORK IN PROGRESS use_pyzor 1 dns_available yes ## Optional Score Increases ## Choose your preferred values... score DCC_CHECK 4.000 score SPF_FAIL 10.000 score SPF_HELO_FAIL 10.000 score RAZOR2_CHECK 2.500 score PYZOR_CHECK 2.500 score BAYES_99 4.300 score BAYES_90 3.500 score BAYES_80 3.000 bayes_ignore_header Received: from mail3.example.com bayes_ignore_header Received: from localhost bayes_ignore_header Received: from mail1.example.com bayes_ignore_header Received: from mail2.example.com
Some notes about this: In zimbra, by default, spam with 15 score of higher is discarded by amavisd. If you want your user receive these mails, you have to modify amavisd.conf settings (/opt/zimbra/conf/amavisd.conf) in order to pass this email.
$final_spam_destiny = D_PASS
To setup DCC: Download dcc from DCC Site
I compile on different system to build an rpm to install in production environment. Use this spec file (rename it to .spec) to build an rpm with the command:
rpmbuild -ba /usr/src/redhat/SPECS/dcc.spec
install it on the production server:
rpm -ivh dcc-x.y.z.rpm
Change /etc/dcc/dcc_conf to read:
Change /opt/zimbra/conf/spamassassin/v310.pre to enable the DCC plugin:
Enable DCC on firewall (UDP/6277 outgoing)
Have fun. I use sqlgrey as greylist server, so I don't need another one. As to me the standard value DCC == 2.5 Spamassassin point is ok, so I do not change it. With SA 3.xx you do not need to use enable_dcc in local.cf. That's the same for razor2 indeed...
It' very simple changing amavis config:
put in /opt/zimbra/conf/amavis.conf*
read_hash(\%whitelist_sender, '/etc/zimbra/whitelist'); read_hash(\%blacklist_sender, '/etc/zimbra/blacklist'); read_hash(\%spam_lovers, '/etc/zimbra/spamlovers');
In /etc/zimbra/* put sender address or domain, one per line. Wildcards allowed. Example:
A spamlovers list is for that accounts that always need to receive all messages, even if spam. According to rfc 2822 postmaster, abuse and other account of this kind should be spam lovers.
I think we should prepare a script to save and restore this config changes upon zimbra updates...