How to convert a MT box in an Anti Spam server with v2.9

Diambil dari http://forum.mikrotik.com/viewtopic.php?t=15721

Hi there, for months I have the idea how to transform one Mikrotik OS in an Anti Spam server. After more than 20 days applying few scripts, firewall rules and address list, I have achieved reduce from 45.000 mails per day to only 11.000/12.000 without many complaints from my customers.

Before continuing, some details about this:

Yes, I know that exists others solutions.
Yes, I know with Linux can obtain the same results.
Yes, I know that it seems a crazy solution.
Yes, I know (in the practice) that this solutions generate a moderate cpu usage. I have a Pentium IV with 75% of cpu usage (this can change with new features from MT… see scripts explanation) and we are a little ISP.
Yes, yes, yes…
but
I use MT from six years ago (when John Tully & Arnis Riekstins answered the company mails themselves) and always I try to resolve any networking necessity whit MT.
I had the trust that can resolve this whit MT.
and after thinking about this, I can’t never sleep all night from many days, so, for my health and wife I made it !!!

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Looking port for spesific application

dari milist tanya jawab

# lsof -i -n -P
COMMAND   PID    USER   FD   TYPE   DEVICE SIZE NODE NAME
ntpd     1748     ntp    4u  IPv4     2487       UDP *:123
ntpd     1748     ntp    5u  IPv6     2488       UDP *:123
ntpd     1748     ntp    6u  IPv4     2489       UDP 127.0.0.1:123
ntpd     1748     ntp    7u  IPv4     2490       UDP 202.156.81.23:123
ntpd     1748     ntp    8u  IPv4     2491       UDP 202.156.81.68:123
sshd     1797    root    3u  IPv6     2669       TCP *:22 (LISTEN)
oidentd  2025  nobody    5u  IPv6     3399       TCP *:113 (LISTEN)

Squid Delaypools

(migrasi dari geocities.com/adilinux)

Another useful squid feature is delay pools. Conceptually, delay pools are bandwidth limitations – “pools” of bandwidth that drain out as people browse the Web, and fill up at a rate you specify – this can be thought of as a leaky bucket that is continually being filled.
This is useful when bandwidth charges are expensive like in indonesia.
Delay pools provide a way to limit the bandwidth of certain requests based on any list of criteria. The idea came from a Western Australian university who wanted to restrict student traffic costs (without affecting staff traffic, and still getting cache and local peering hits at full speed).

To enable this, configure squid with the –enable-delay-pools option. There are 3 classes of delay pools – class 1 is a single aggregate bucket, class 2 is an aggregate bucket with an individual bucket for each host in the class C, and class 3 is an aggregate bucket, with a network bucket (for each class B) and an individual bucket for each host. Read more »