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In This Chapter:
SpamAssassin
Overview
SpamAssassin is a powerful tool for eliminating unsolicited
email (spam) from your incoming mail. Using a wide range of
rules and filtering methods, it scans incoming emails and
accurately detects spam. SpamAssassin does not require you
to install any software on your computer. Instead, it runs
on the server-side, scanning and filtering email before it
is delivered to your mailbox.
SpamAssassin subjects every incoming email to three levels
of spam tests:
- Header Analysis. Spammers often forge
return addresses, and add bogus entries to the headers of
their emails. This is done both to fool you into thinking
that the email is valid, and to make it harder to determine
the actual source of the email. Spam Assassin knows what
to look for in these headers, and can quickly identify false,
invalid, or misleading information.
- Text Analysis. Spam emails often have
characteristic styles, phrases, and disclaimers in them.
SpamAssassin attempts to spot some of these clues. SpamAssassin
also scans the body of each email for links to known spammer
websites.
- Blacklists. SpamAssassin compares each
email to the lists maintained on major Real Time Blacklist
servers (RBLs). If an email is sent from a domain or server
in one of these blacklists, there is a good possibility
that it is spam.
Each test uses hundreds of rules that indicate whether an
email might be spam. Each rule it finds is assigned a "point"
value. When the total points of an email exceed your acceptable
limit, the email is considered spam.
When an email is considered spam, SpamAssassin can handle
it in a variety of ways depending on your specific preferences.Using
the "What to do with Spam" options, you can have
spam delivered normally, have it delivered to a special "spam"
mailbox, or have it automatically deleted. When you have the
mail delivered normally, or to the "spam" mailbox,
you can also specify how that email gets delivered:
- rewrite_subject: the spam email will
have a "*****SPAM*****" flag placed in its subject
line.
- report_safe: a new spam report email
is created containing the full details of the spam filter’s
decision. The spam email is attached to this report email
in its original state. This option may be used. The original
email is attached as a message/rfc822 MIME part which ensures
that it is completely preserved, not easily opened, and
much easier to recover.
- If you disable both the rewrite_subject and report_safe
options, then the spam email will have “X-Spam”
tags inserted in its message headers, however, the subject
line will not be altered in any way, and the email will
not be attached to a spam report email.
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How
to Setup SpamAssassin
Once you have installed the proper SpamAssassin package,
you must enable the filter. To do this, go to the "SpamAssassin"
section of your Control Panel. From there, select "On"
and click the "Apply" button. Your SpamAssassin
filter has now been enabled with the following default settings:
- SpamAssassin will let spam go to your mailbox, where you
will delete manually.
- Filter Sensitivity is set to 6
- Spam Reports are generated with the original email as
an attachment
- The text "*****SPAM*****" is added to the subject
line of the report email.
Step 1.
Select what you would like SpamAssassin to do with spam emails.
If you are just getting started with SpamAssassin, it is recommended
that you select one of the first two options. This way, you
can ensure that legitimate emails are not getting accidentally
caught and deleted by SpamAssassin. As time passes your white-list
becomes more extensive, and your SpamAssassin filter gets
smarter. At this time, you may want to consider switching
this setting to automatically delete spam emails.
Step 2.
Set your filter sensitivity. Sensitivity ranges from 2 to
12. This value refers to the minimum score required for an
email to be flagged as spam. Therefore, the lower this number,
the more sensitive your filter becomes. Initially, you should
select a setting somewhere in the middle (5-8). If you receive
a large amount of spam emails, you should make your filter
slightly more sensitive (closer to 5), while if you only receive
a few spams, you should set your sensitivity closer to 7 or
8. It is a good idea to adjust your filter sensitivity until
you find the perfect fit.
Step 3.
By default, SpamAssassin flags all suspected emails as spam
by placing a “*****SPAM*****” tag in their subject
line. Also by default, SpamAssassin creates a spam report
email and attaches the original spam email to this report
before sending it to your inbox. If you wish to disable either
of these options, select to do so in the “Reporting
Customization” section of your SpamAssassin manager.
Step 4.
Immediately create your White List, Black List (if necessary)
and any other message rules you desire. Use the “Add
Rules” section to do this. To create a new rule, select
the “Action”, place the email address, domain
name, or pattern into the rule and click “Add Rule”.
Once you have completed these steps, SpamAssassin will effectively
filter at least 95% of the spam emails sent to your domain.
Other settings in the Control Panel allow you to customize
where SpamAssassin places its reports, enable and disable
HTML conversion, and create rules for your White and Black
Lists.
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Control Panel
Configuration Options
The SpamAssassin Control Panel allows you to customize the
functionality of your SpamAssassin filter. These options give
SpamAssassin increased flexibility and allows it to adapt
to your specific needs.
The following is a detailed description of each option available
to you through this control panel.
Spam Filtering
Once your SpamAssassin filter has been enabled, this is the
first option you will see in the Control Panel. If you wish
to disable the SpamAssassin filter completely, select "Off"
and click the "Apply" button. This will effectively
turn spam filtering off on your account.
What to do with Spam
In this section, you can specify the action that SpamAssassin
takes when it determines that an email is spam. There are
three options:
- Do Nothing - this will deliver the email
to your regular inbox with whatever Report Customization
preferences you have selected.
- Move - this will deliver the email to
a special "spam" mailbox. Mail is automatically
deleted from the "spam" mailbox after 30 days.
This gives you the chance to login to webmail, or download
the "spam" mailbox to your computer to occasionally
check its contents.
- Delete - this will immediately delete
any email identified as spam. This option is only recommended
for users who have a thorough White-list, and have been
using SpamAssassin for a while.
Filter Sensitivity
The sensitivity of your filter is the minimum
score that you would like an email to have in order for it
to be labeled spam. For example, if you want any email scoring
6 or greater to be labeled as spam, set your filter sensitivity
to 6. To make your filter more sensitive, decrease your filter
sensitivity level. This way, a lower score is required for
an email to be flagged as spam. If you wish to make your filter
less sensitive, simply increase its filter sensitivity number.
It is suggested that you keep your filter sensitivity
level somewhere in the middle range. This way the majority
of spams will be caught while few legitimate emails will be
mistaken for spam. Adjust your filter sensitivity level according
to the amount of spam you receive. For large volumes of spam,
a more sensitive filter may be needed, while if you receive
few spams, you can keep your sensitivity relatively low.
Reporting Customization
This option has two sections. The first "rewrite_subject"
allows you to enable and disable the "*****SPAM*****"
subject line flagging. The second "report_safe"
enables and disables the generation of a Spam Report email
with the original email as an attachement.
- rewrite_subject
- Off: the subject line will remain
intact
- On (default): the subject line of
suspected spam will include the "*****SPAM*****"
text
- report_safe
- Off: no spam report email is generated,
instead, the original email is delivered with some additional
"X-SPAM' headers. No changes are made to the body
of the email.
- On (default): A full Spam Report
email is generated with the scanning details with the
original email as an attachment.
Add Rule
The "Add Rule" section allows you to create and
administer to your own White and Black Lists. The instructions
found in this section make it self explanatory.
To add an address, domain, or sub-domain to your White List,
select the "Accept Mail From" rule, enter the address,
and click "Add Rule".
Conversely, to add someone to your Black List, select the
"Reject Mail From" rule, enter the address, domain,
or sub-domain, and click "Add Rule".
To Disable SpamAssassin Filtering for a specific email address
in your account, use the "Accept Mail Sent to" rule.
The "Current Rules" section displays all of the
rules currently stored in your filter. You can use the "Delete
Rule" link to remove any of these. This screenshot displays
an example of each rule:
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