SmarterMail 4.x Help
This documentation is for a product that is no longer supported by SmarterTools.

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

Name Web Site DNS Server
SpamCop http://www.spamcop.net bl.spamcop.net
SpamHaus SBL+XBL http://www.spamhaus.org sbl-xbl.spamhaus.org