184 Napier Street, South Melbourne, 3205
Tel: 61-3-9699 8844, Fax: 61-3-9690 5331
* * * SPAM AND ANTISPAM * * *
Copyright © Micronica
Our Micronica Spam Blacklist has been primarily designed from the ground up
using the long established "sendmail". You can also use the Spam Blacklist
with Postfix instead:
How to use Micronica Spam Blacklist with Ubuntu Postfix
The "sendmail" /etc/mail/access list is basically same as the "Postfix"
/etc/postfix/sender_checks list. Similar Block or Allow syntax.
In /etc/postfix/main.cf add:
smtpd_sender_restrictions = check_sender_access
Then copy this blocking list to /etc/postfix/sender_checks
Then install "postmap" and create or "compile" a map file:
sudo postmap sender_checks
Then restart postfix
sudo /etc/init.d/postfix restart
If you want to include your own seperate "Whitelist" to ALLOW such things as spamming "freemail.com" domains or IPs thats easy too! Simply concatenate your own list
to our Micronica blacklist, such as:
Or create a totally seperate "White" list:
Create the Whitelist /etc/postfix/rbl_override
Then run: postmap /etc/postfix/rbl_override
Then in /etc/postfix/main.cf search for the smtpd_recipient_restrictions
check_client_access hash:/etc/postfix/rbl_override after reject_unauth_destination, but before the first blacklist.
Then restart postfix
sudo /etc/init.d/postfix restart
Here are some suggestions for Internet Service Providers (ISP) and System
Administrators on how to tackle the spam problem. There is lots of advice
out there about the installation of Email Filters. But the following are
some extra points we have found from experience to be helpful.
1) If you are a firm believer in "Email Filtering"
ensure your spam filtering is "symmetrical" for both send and receive directions.
To avoid the ironic situation where we cant forward you full details of a spam that
YOU sent out. Think about it...its inconsistent and dumb that YOU would SEND
OUT an email with spam that you would NOT want to RECEIVE YOUSELF ! Its
amazing that many Email Service providers such as Google, Gmail and many
ISP's dont do this! Even with risk of "false positive" to your own, possibly intentional or unintentional spamming,
customers. This makes some of the "Big Email Services" such as gmail.com,
hotmail.com, yahoo.com etc also some of the worst SOURCES of spam...with their own
customers obliviously saying "oh but i hardly ever
get any spam" whilst those service providers are gingerly sending OUT bucket
loads of it. In effect they are supporting spam.
2) To allow VICTIMS of spam and ISPs such as us to forward
you the full contents of the offending spam and alert you to the problem
you could make your support email addresses such as "email@example.com,
firstname.lastname@example.org, email@example.com open to ALL email content rather than
rejecting the emails with the spam evidence. It's EASY to do and from our experience spammers tend NOT to target
those email addresses as they know it will alert support staff of spams.
Most spammers are not that dumb ;-)
3) If you are one of those email service providers
who allows anyone anywhere in the world to log in with a simple username and password to send
emails from your server then to avoid having your customers email accounts
persistantly hacked and used to send spam, which happens every minute of the day,
you could restrict user smtp access to only certain COUNTRIES and block the common nasty ones
ending in .ru (russia), .mx (mexico), .pl (poland) etc. That would cut
your hacker risk by a large percentage right away. We decided long ago to tell
customers to use widely available free smtp software on their computers or use their LOCAL ISP
smtp server to send emails. Yeah its a bit of a nuisance having to spend 5 seconds to click and run
the smtp sender on the computer or to set it up to run at bootup. But it's just simply to risky to allow
EVERYONE smtp server access in even the most irrelevant places on earth who happens to have hacked a username and
4) You could limit spam blocking based on SOURCE
IP ADDRESS rather than CONTENT like we found many years ago to be much more effective.
As we found text filtering just really doesnt work. Text "Filtering" results in precisely the
situation that spam victims can not email you the offending email! So you
end up in a "Catch 22" situation. And Spam FILTERING detects the spam AFTER accepting it which is already too late.
The spammer effectively thinks maybe you like spam :) He never waits for the
possible rejection from the filter software. Hence we prefer spam BLOCKING
based on source rather than spam FILTERING based on content. It also cuts your
internet traffic by a huge amount ;-)
FYI you can see our PROPRIETARY international spam blocking list based on
SOURCE blocking rather than filtering at
this is about HALF of our total blocking list which is FREE for people to
download and use. for the other half of our blocking list which is the
intelligent Automatically updated blocking list which updates every 10
seconds, there is a very small fee.
Hope the above proves useful in the good fight against the biggest problem
on the internet...Spam! ;-)
- Internet and Computer Services -
184 Napier Street, 14 Howe Crescent, South Melbourne, 3205 Victoria, AUSTRALIA
Tel:(03) 96998844 Fax:(03) 96905331
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