Spam Control
FIRST PUBLISHED HOWTO: SPAM CONTROL ON LINUX MAIL SERVERS
Below is a solution to inhibit the delivery of most of the spam that might hit your mail server. It's an ongoing development of mine that has been shared with Linux usergroups. I'm posting it here so that it has a home on my personal website as well.
So, I began to do some research and have come up with a modified main.cf for Postfix and a need to install Postgrey:
1) Install Postgrey
apt-get install postgrey
Postgrey will have a delay of 5 minutes by default on email going to your mailbox. If this is too long, edit the /etc/default/postgrey file by adding "--delay=120" where 120 is seconds.
2) Restart the Postgrey server.
/etc/init.d/postgrey restart
3) edit the Postfix main.cf. We will be adding several things including the Postgrey configuration.
# See /usr/share/postfix/main.cf.dist for a commented, more complete version
# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
biff = no
# appending .domain is the MUA's job.
append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
readme_directory = /usr/share/doc/postfix
# TLS parameters
smtpd_tls_cert_file = /etc/postfix/smtpd.cert
smtpd_tls_key_file = /etc/postfix/smtpd.key
smtpd_use_tls = yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
myhostname = my.derekgordon.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = my.derekgordon.com, localhost, localhost.localdomain
relayhost =
mynetworks = 127.0.0.0/8 [::1]/128 66.118.142.78
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
html_directory = /usr/share/doc/postfix/html
virtual_alias_domains =
virtual_alias_maps = proxy:mysql:/etc/postfix/mysql-virtual_forwardings.cf, mysql:/etc/postfix/mysql-virtual_email2email.cf
virtual_mailbox_domains = proxy:mysql:/etc/postfix/mysql-virtual_domains.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailboxes.cf
virtual_mailbox_base = /var/vmail
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
smtpd_sasl_auth_enable = yes
broken_sasl_auth_clients = yes
smtpd_sasl_authenticated_header = yes
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, check_recipient_access mysql:/etc/postfix/mysql-virtual_recipient.cf, reject_unauth_destination, check_policy_service inet:127.0.0.1:60000, reject_rbl_client zen.spamhaus.org, reject_rbl_client dnsbl.sorbs.net, reject_rbl_client bl.spamcop.net, reject_rbl_client combined.rbl.msrbl.net, reject_rbl_client multihop.dsbl.org, check_recipient_access regexp:/etc/postfix/spamtrap, permit
smtpd_tls_security_level = may
transport_maps = proxy:mysql:/etc/postfix/mysql-virtual_transports.cf
relay_domains = mysql:/etc/postfix/mysql-virtual_relaydomains.cf
relay_recipient_maps = mysql:/etc/postfix/mysql-virtual_relayrecipientmaps.cf
virtual_create_maildirsize = yes
virtual_maildir_extended = yes
virtual_mailbox_limit_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailbox_limit_maps.cf
virtual_mailbox_limit_override = yes
virtual_maildir_limit_message = "The user you are trying to reach is over quota."
virtual_overquota_bounce = yes
proxy_read_maps = $local_recipient_maps $mydestination $virtual_alias_maps $virtual_alias_domains $virtual_mailbox_maps $virtual_mailbox_domains $relay_recipient_maps $relay_domains $canonical_maps $sender_canonical_maps $recipient_canonical_maps $relocated_maps $transport_maps $mynetworks $virtual_mailbox_limit_maps
smtpd_sender_restrictions = check_sender_access mysql:/etc/postfix/mysql-virtual_sender.cf
smtpd_client_restrictions = check_client_access mysql:/etc/postfix/mysql-virtual_client.cf
maildrop_destination_concurrency_limit = 1
maildrop_destination_recipient_limit = 1
virtual_transport = maildrop
header_checks = regexp:/etc/postfix/header_checks
mime_header_checks = regexp:/etc/postfix/mime_header_checks
nested_header_checks = regexp:/etc/postfix/nested_header_checks
body_checks = regexp:/etc/postfix/body_checks
content_filter = amavis:[127.0.0.1]:10024
receive_override_options = no_address_mappings
message_size_limit = 0
disable_vrfy_command = yes
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks, reject_invalid_hostname, permit
From a generic main.cf found in the Debian Lenny installation, I added/modified the BOLD areas.
4) Create a file named "spamtrap" in the /etc/postfix/ directory. This serves as a filter. If spam is emailed to this address and other addresses on your machine, it will drop that email so that it doesn't get to any other mailboxes.
spamtrap file looks like this:
/emailcontrol.*@derekgordon\.com/ DISCARD
This is regexp so the slashes have to be used. My filter email is [email]emailcontrol@derekgordon.com[/email] so edit accordingly and place in the spamtrap file!!!
Side note: Do not create this mailbox using ISPConfig. There is absolutely no reason for it to exist on your mailserver. It's a fake address meant to catch annoying spam.
5) Restart Postfix
/etc/init.d/postfix restart
ALL DONE!!! THE spam has decreased about 600% in the first full day of use. My personal email box, which was receiving 15 - 20 spam emails a day without Postgrey now receives 1.
If you want to leave feedback on this method, or have questions, you may post those to my original thread at http://www.howtoforge.com/forums/showthread.php?t=48608