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Anti-Spam Administration
SmarterMail's anti-spam features allow you to be as aggressive as you want when
combating spam. The Anti-Spam Administation page is separated into tabs to make
configuring the system easier. These tabs are briefly explained below, with detailed
explanations afterward.
- Spam Checks - Check the spam options that you want to enable for filtering
(a point-based weighting system for filtering spam) and for blocking at the SMTP
level. Weights can also be edited for the various checks from this tab.
- Filtering - Choose the default weight thresholds and actions for various
spam levels for filtering. Users can override these settings if you permit them
to.
- SMTP Blocking - Set the weight to use as a threshold on this tab. Enabling
this option will block email at the SMTP delivery level if too many spam checks
fail.
- Options - This tab contains options relating to the processing of spam and
overridability.
In short, when an email comes in, spam checks are run on it. The checks that fail
add points to the email, which then put the email into a category of spam probability.
Spam Checks
Due to the flexible nature of SmarterMail's Anti-Spam setup, spam checks can influence
the spam decision as much or little as you want. When spam protection runs on a
particular email, all enabled spam checks are performed on the email. The total
weight of all failed tests is what comprises the spam weight for the email. A spam
probability level is then assigned to the email using the settings in the Filtering
tab.
Note: Only enabled spam checks are used when calculating spam weight. To enable or
disable a check, click on the appropriate checkbox next to it and click save.
The different types of Spam Checks are shown below. In most cases, clicking on the
edit link will allow you to set various properties about it.
Declude
Declude integration allows you to use Declude products in conjunction with the SmarterMail
weighting system. Configuration of Declude is done through the Declude product,
and all you need to do in SmarterMail is enable the spam check.
SpamAssassin
SmarterMail can use SpamAssassin with its weighting system. By default SpamAssassin
will run on 127.0.0.1:783. Additional servers can be setup from the Security->SpamAssassin
menu option.
Low Probability of Spam - The weight that will be assigned if SpamAssassin
determines a low probability of spam.
Medium Probability of Spam - The weight that will be assigned if SpamAssassin
determines a medium probability of spam.
High Probability of Spam - The weight that will be assigned if SpamAssassin
determines a high probability of spam.
Timeout - The timeout that SmarterMail will impose on a server if it cannot
connect.
Maximum Attempts per Message - This will designate how many times SmarterMail will attempt to acquire a SpamAssasasin score before it gives up on that email.
Custom Headers
Email can be assigned spam weight based on headers in the message. Use this selection
to configure weights for custom headers.
Header - The custom header to search for in the e-mail message.
Value - The value of the custom header.
Weight - The amount to add to the e-mail message's spam weight.
Bayesian Filtering
Bayesian Filtering uses statistical analysis to identify whether or not an email
appears to be spam. Tying it together with blacklists and SPF allows you to be quite
sure that email is or is not spam.
Weight - The default weight for this spam check. If an email has a high probability
of being spam based on its content, this is the value that will be added to the
message's total spam weight.
Max memory to allocate for filtering - Bayesian Filtering can be memory intensive.
As a result, SmarterMail allows you to configure the maximum resources that will
be dedicated to Bayesian Filtering. In general, the more memory you reserve for
Bayesian Filtering, the more accurate the results will be.
Messages required for filter update - Once this number of messages have been
processed as known-good or known-spam email, SmarterMail will re-analyze the filters
to help your system protect against new spam threats. In this way, Bayesian Filtering
can become more tailored to handle the mail of the domains on the server.
SPF (Sender Policy Framework)
SPF is a method of verifying that the sender of an email message went through the
appropriate email server when sending. As more and more companies add SPF information
to their domain DNS records, this check will prevent spoofing at an increasing rate.
Pass - Indicates that the email was sent from the server specified by the
SPF record (more likely good mail). The weight you set may be 0 (for no effect)
or a negative number, thereby reducing the spam rating.
Fail - Indicates that the email was sent from a server prohibited by the
SPF record (highly likely spam). Set this to a relatively high weight, as the probablility
that the email was spoofed is very high.
SoftFail - Indicates that the email was sent by a server that is questionable
in the SPF record. This should either be set to 0 or a low spam weight.
Neutral - Indicates that the SPF record makes no statement for or against
the server that sent the email. Except in very special circumstances, leave this
set to 0.
PermError - Indicates that there is a syntax error in the SPF record. Since
SPF is relatively new, some domains have published improperly formatted SPF records.
It is recommended that you leave this at 0 until SPF becomes more popular on the
internet.
None - Indicates that the domain has no published SPF record. Since SPF is
relatively new, many legitimate domains do not have SPF records. It is recommended
that you leave this at 0 until SPF becomes more popular on the internet.
Reverse DNS
Reverse DNS checks to make sure that the IP address used to send the email has a
friendly name associated with it.
Weight - The default weight for this spam check. If an email sender does
not have a reverse DNS entry, this is the value that will be added to the message's
total spam weight.
RBL Lists
RBL Lists (also known as IP4R Lists) are publicly accessible lists of known spammer
IP addresses. These lists can be a very important part of spam protection. To attach
to a list, click on Add List. Some common RBL lists are shown at the bottom of this
topic.
Name - A friendly name for the list that will help you and your customers
identify it.
Weight - The default weight for this spam check. If an email sender is listed
with the spam list, this is the value that will be added to the message's total
spam weight.
DNS Server - Spam lists operate through DNS. As a result, each list provider
gives out a DNS server that contains the blacklist. Enter it in this box.
Description - This field allows you to store additional information about
the list.
Filtering
Emails are filtered into one of four categories based on their total weight. If
a weight is equal to or higher than a certain category, then it is assigned that
probability of being spam. Use the Actions tab to define the weight thresholds and
the default actions at each level.
Weight Threshold - The email is sorted into probability levels based on the
weight threshold values.
Action - The action to take when a message ends up with this probability.
SMTP Blocking
This tab allows you to set up extra spam checks that block emails at delivery if
a certain amount of spam checks fail.
Enable SMTP Spam Blocking - Check this box to turn on this feature.
SMTP Block Threshold - An email must score this value or higher in order
to be blocked. The score is established by the settings on the Spam Checks tab.
Options
Allow domains to override weights - Many domain administrators have their
own opinions on what spam checks work best for their domain. Check this box to allow
them to override the spam options if they wish.
Skip spam filters on intra-domain email - Checking this box will skip spam
filtering when messages are sent from from within the same domain (e.g. user1@example.com
to user2@example.com).
Adding and Editing RBL Lists
To add a new RBL list or edit existing ones, click on the Edit RBL Lists button.
Common Spam Lists