Ubuntu Manpage: mailfilterex - Mailfilter configuration file examples

NAME

       mailfilterex - Mailfilter configuration file examples

SYNOPSIS

       $HOME/.mailfilterrc examples

DESCRIPTION

       For  a  description of the rcfile format and its keywords see the mailfilterrc(5) man page
       or get a basic set of options from either the INSTALL file or the doc/  directory  of  the
       Mailfilter distribution.

       This  man  page  contains  several  configuration examples and real-life use cases for the
       Mailfilter program.

EXAMPLES

If not stated otherwise, the following examples assume you are using extended Regular
Expressions, compared to Mailfilter's default, basic type. General information on Regular
Expressions can be found in the regex(7) man page or in any good book on UNIX/POSIX. You
could also use slightly modified examples from procmail(1) if it is available on your
system.

Filtering Domains
To create a very restrictive set of filter rules at least two keywords should be used:
ALLOW and DENY. DENY could match all messages coming from an annoying public mail service,
while ALLOW matches messages from a good friend who also uses this annoying public mailer.

DENY = "^From:.*public-mail\.com"
ALLOW = "^From:.*friend@public-mail\.com"

These two lines are enough to block all but your friend's e-mail from the public-mail.com
domain.

Case Sensivity
In general case-sensivity is controlled by the REG_CASE keyword. Having Mailfilter treat
expressions case-insensitive is almost always more efficient.

REG_CASE = "no"
DENY = "^Subject:.*win money"

In this example Mailfilter would delete all messages with subject lines like `WIN MONEY',
`Win Money' or any other mix of capital and non-capital characters. REG_CASE makes filters
ignore the case.

A more complex set up can be achieved by additionally using the DENY_CASE keyword.

DENY_CASE = "^Subject:.*BUSINESS"

In this example only e-mails that have `BUSINESS' in their subject match the filter, even
though in general Mailfilter ignores the case. So in this example all messages with
`business' or `Business' in their subjects would not be affected by this filter.

Such an option is very useful if you are not interested in commercial bulk mail that
offers amazing business opportunities, but in all your business partners who contact you
by e-mail.

Defining Friends
The keyword ALLOW can be used to override any spam filters. Similar to the earlier example
ALLOW defines a `friend'.

ALLOW = "^Subject:.*mailfilter"

Adding this rule to the rcfile would mean all messages that contain anything about
Mailfilter in their subject lines can pass the spam filters. But even friends tend to send
large e-mails sometimes to share their joy about the latest joke that just made the round
in their office. In such cases a limit can be defined that affects particularly `friends'.

MAXSIZE_ALLOW = 500000

Setting MAXSIZE_ALLOW to 500000 means no message can be larger than 500 kBytes. (Scanned
`office-jokes' are usually around that size.)

Negative Message Filters
In order to create a very restrictive spam protection it can be more useful sometimes to
define which e-mails should not be deleted instantly and consequently get rid of messages
that can not be matched to this criterion - rather than vice versa. This can be achieved
by using negation. The typical use case is looking at the message tags `To:' or `Cc:' of
an e-mail.

DENY <> "^(To|Cc):.*my-email@address\.com"

Having added such a filter to your personal rule set keeps away a lot of spam that is not
directly addressed to your e-mail account. Since this is a very aggressive way of
filtering, you are well advised to keep your `friends list' up to date. Also note that the
above example, using the logical OR operator, works only with extended Regular
Expressions.

Scores
Instead of setting up spam filters, it is also possible to define scores which can be
accumulated until a certain threshold is reached. This is very useful to delete
advertisements on mailing lists, for instance. Highscore marks the threshold:

HIGHSCORE = 100
SCORE +100 = "^Subject:.*viagra"
SCORE +100 = "^Content-Type:.*html"
SCORE -100 = "^(To|From):.*my_mailing_list"

This simple example is useful to delete mails with a score greater than 100, i.e. if
someone sends an HTML mail to my_mailing_list, the message will reach score 0. However,
should an HTML mail regarding Viagra reach the list, then the message will classify as
spam, because it reached an overall score of 100.

The MAXSIZE_SCORE keyword can be used to add to the accumulated score for an e-mail. The
following will cause all emails not directly addressed to the recipient and greater than
60000 bytes in size to be deleted (a useful way of rejecting many common MS targeted worms
and trojans which can clog up your inbox).

HIGHSCORE = 100
MAXSIZE_SCORE +50 = 60000
SCORE +50 <> "^(To|Cc):.*my-email@address\.com"

This is a less aggressive way of dealing with e-mail sizes than the using the MAXSIZE_DENY
keyword. Note that this example (by using the expression (To|Cc):.*my-email@address\.com)
works only with extended Regular Expressions.

General Message Size Limits
It is always a good idea to define a very general size limit for e-mails. Mailfilter uses
the keyword MAXSIZE_DENY for that purpose.

MAXSIZE_DENY = 200000

Setting it to 200 kBytes can save you a couple of hours, depending on how much mail you
get everyday. Messages bigger than that get deleted on the server, unless they match any
of the ALLOW rules. To achieve maximum efficiency it makes sense to use both MAXSIZE_DENY
and MAXSIZE_ALLOW. No one should block up your mail box, no `friends', no others.

A rule of thumb is to be twice as tolerant towards friends than you are towards anonymous
people.

Dealing with Duplicates
Most people want to download a message only once, even though it might have been sent to
two or three of their accounts at the same time. The simple line

DEL_DUPLICATES = "yes"

will take care of duplicates and makes sure that only one copy of a message has to be
delivered.

Normalisation of Message Subjects
Every now and then some clever sales person comes up with the brilliant idea to wrap spam
in funny little characters. If you get a message with a subject line similar to this one
`,L.E-G,A.L; ,C.A-B`L`E, .B-O`X`', then ordinary filters would fail to detect the junk.

NORMAL = "yes"

Adding this directive to the rcfile tells Mailfilter to `normalise' subject strings, i.e.
leave in only the alpha-numeric characters and delete the rest. `,L.E-G,A.L; ,C.A-B`L`E,
.B-O`X`' would then become `LEGAL CABLE BOX' which can easily be matched to a spam filter.

Note that Mailfilter first tries to match the original subject string, before it checks on
the normalised one.

Control Mechanism
Since Mailfilter deletes e-mails remotely, before they have to be downloaded into the
local machine, it is also important to know what is going on while the program is being
executed. The least you should do is define a proper level of verbosity and a log file.

LOGFILE = "$HOME/logs/mailfilter-`date +"%h%y"'"
VERBOSE = 3

Level three is the default verbosity level. Using it, Mailfilter reports information on
deleted messages, run-time errors and dates to the screen and the log file.

You can use `command' to embedd shell skripts into your path names. In the above example
it is used to store log files separately for each month and year.

Extended Regular Expressions
For advanced applications, the basic Regular Expressions are typically not sufficient. If
you know the syntax and usage of the extended expressions, it is almost always a good idea
to set REG_TYPE accordingly.

REG_TYPE = "extended"

Extended expressions are more flexible, but also more sensitive towards syntax errors and
the like. Examples in this man page all use extended type.

NOTES

       If you are new to Regular Expressions and new to Mailfilter, you might want to  experiment
       a  bit, before you accidently delete messages for real. For such cases Mailfilter provides
       two keywords. TEST can be used to only simulate the deletion of messages and  SHOW_HEADERS
       stores all the e-mail headers that get examined by the program.

              TEST = "yes"
              SHOW_HEADERS = "$HOME/logs/mailfilter-headers.txt"

       Use  this  setup if you are not yet comfortable with the concept of spam filtering. It may
       help to understand Regular Expressions better and how to use them.

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