Email filtering allows you sort incoming e-mails into various
folders within your e-mail program. For example, you could
set up a filter so that any any messages from yourfriend@yourfriendsserver.com
would be placed in a folder containing only your friend's
e-mail. Filters are very flexible - they can include part
or all of the "from:" and "to:" address fields, or just specific
words within the subject or body of the message. After an
e-mail filter has been set up, all e-mail sent to you is
automatically filtered into the appropriate folders.
A common use for mail filters is to sort spam into a different
folder than the rest of your messages. After you have read about
how to set up filters in your version Outlook, follow the
instructions below to set up a spam filter.
Acme Internet's mail server has a built in spam filter called
Declude
that can filter your mail even before you download it to your
hard disk. To use this filter, you will need to log in to
your email account through the
Webmail system and
modify your domain filters. (For help on using Webmail,
click here.) Once you have
logged in to your Webmail account, select "Domain Filters" from
the menu on the right side of the screen.
A new window should appear, allowing you to enter a rule for
filtering your e-mail. To set up a spam filter, modify the
settings to look like the ones below:
This will filter spam using the Declude Virus software on Acme
Internet's mail server. All mail that the software detects
as spam will be filtered into a new folder called "spam."
How does it work?
The Declude Virus scanning system uses headers to mark messages
that are sent from spammers. "Headers" is a email field,
just like the "to:" and "from:" fields, but they are typically
hidden in the email. All messages sent to any account
hosted by Acme Internet are scanned by the Declude Virus program
and marked with the appropriate headers. The one you see
in the example above is a standard header for an message that is
determined to be spam by the Declude Virus software. It is
merely one of dozens of
available tests. You may enter a number of other
headers in your mail filter that may help to filter your mail
more successfully.
A couple examples are:
X-RBL-Warning: SPAMCOP
X-RBL-Warning: WEIGHT13
SPAMCOP
The SPAMCOP test checks the SPAMCOP blacklist at
http://www.spamcop.net
The SPAMCOP service is a free Internet user community driven
spam reporting and blocking service.
WEIGHT
The WEIGHTING test assigns each of the other 100+ tests a
"weight" (kind of like a score or a negative rating). The WEIGHT
assigned for flunking a particular SPAM test can range from 1
(minor infraction) to 10 (really smells bad - high likelihood of
SPAM).
The more tests an email flunks, the higher the weight/score it
will receive. Once an email fails enough tests to reach a
certain "trigger" value, the WEIGHTING test will mark the E-mail
as spam. This will allow you to use tests that have high false
positive rates, while not worrying as much about losing
legitimate mail. Using the WEIGHT system an email needs to flunk
several tests in order to be flagged as SPAM.
The exact WEIGHT for each SPAM test is configured on the mail
server within the Declude configuration files and cannot be set
by the user. We tend to use the defaults suggested by Declude.
Setting the WEIGHT at 13 is a good place to start. If a user
wishes to be more lenient with spam rules, they can try setting
the WEIGHT value to 20 (allows the email to fail one or two more
tests before being marked as SPAM).
Filtering SPAM is not
an exact science. It involves a ongoing process of trial and
error to customize your mail processing rules based on your
preferences. Over a period of time you will find that
certain tests are more effective than others for your
particular situation when blocking unwanted email.
NOTE: Using the Declude Virus filtering system as
mentioned above will filter spam messages into a spam folder.
It will not delete them. This means that after
awhile the messages may fill up your disk quota if you do not
periodically delete them from your spam folder.
You may also download the messages in the spam folder to
your Microsoft Outlook account on your computer.
For directions on how to
download the messages in your spam folder, click here.
