(postfix) SPAM filter?

[Jack Raats]

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Hi Sten and the rest,

> We have a need for a relatively painless anti-spam solution that would
> reduce the amount of incoming spam (via postfix mail router). The problem
> is that i have little knowledge on what this actually means. Googling
> reveals a whole "universe" of interesting ways but what should i pursue?
> The things that are important to me is:
>
> * Once it is setup then it would require no additional maintenance.
> * Potential spam messages are marked with a special header that can be
> filtered on user discretion on their local mail client software.
>
> Neither performance, scalability, license nor cost is of much importance
> to me at this point.

I have a different approach. I refuse all connections from ip's which
reverse DNS points to costumers of providers.
This gives a huge reduction of botnets.
Below my helo_checks and client_checks. Ofcourse use it for your own risk!
Besides this method I also use rbls's, greylisting, clamsmtpd, clamav,
procmail and spamassasin

#######################################################################
# helo_checks.pcre
#######################################################################
/^[0-9.]+$/             REJECT Please use your ISP's outgoing mail server -
HA
/^\|/                         REJECT Please use your ISP's outgoing mail
server - HB
/^[\d\.]+$/               REJECT Please use your ISP's outgoing mail
server - HC

# H1 adsl,dial,dhcp,cable,retail,dynamic in helo
/(adsl|dial|dhcp|cable|retail|dynamic)/i     REJECT Please use your ISP's
outgoing mail server - H1

# H2 customer,static,kabel in helo
/(customer|static|kabel)/i                           REJECT Please use your
ISP's outgoing mail server - H2

# H3 12345
# /\d{5}/                                                       REJECT
Please use your ISP's outgoing mail server - H3

# H4 123-123-123
/\d{1,3}-\d{1,3}-\d{1,3}/                              REJECT Please use
your ISP's outgoing mail server - H4

# H5 123.123.123
# /\d{1,3}\.\d{1,3}\.\d{1,3}/                         REJECT Please use your
ISP's outgoing mail server - H5

#######################################################################
# client_checks.pcre
#######################################################################

# C1 adsl,dial,dhcp,cable,retail,dynamic in hostname
/(adsl|dial|dhcp|cable|retail|dynamic)/i     554 Please use your ISP's
outgoing mail server - C1

# C2 customer,static,kabel in hostname
/(customer|static|kabel)/i                           554 Please use your
ISP's outgoing mail server - C2

# C3 123456
/\d{6}/                                                          554 Please
use your ISP's outgoing mail server - C3



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