Messiah College Spam Filter User's Guide

Spam, also known as unsolicited commercial email, is one of the foremost problems with Internet mail today. Email accounts that have been in use for more than a few months can quickly become inundated with spam. This spam causes wasted user's time and consumes network resources.

Introducing SpamAssassin

SpamAssassin is a mail filter which attempts to identify spam using a variety of methods, including text analysis, realtime blacklists, distributed databases, and message signatures. Using its rule base, it uses a wide range of heuristic tests on mail headers and body text to identify spam. Spam is identified by assigning it a score. This score can be used to determine "how much" the message looks like spam.

Once identifying a message as spam, SpamAssassin will either delete the message outright, or tag it as spam, causing GroupWise to file the message in your Junk Mail folder. No spam filter is perfect, and SpamAssassin is no exception. Initially, SpamAssassin will catch about two-thirds of your spam. This means you will still see some spam. The effectiveness will improve as SpamAssassin begins to learn what your typical mail looks like. Sometimes SpamAssassin will incorrectly mark regular mail as spam (called a "false positive"). For this reason, it's important to periodically check your Junk Mail folder for messages you want.

Using the Spam Filter

The spam filter is enabled for every Messiah College email user, both students and employees, so you don't need to do anything to start using it.

False Positives

It is often the case that SpamAssassin will make a mistake. Most often, it will fail to identify a spam message as spam. This is annoying, but at least you don't miss legitimate mail because of it. Unfortunately, sometimes SpamAssassin marks a real message as spam. Because of this, users of the spam filter should be careful about checking their spam messages, especially when first starting on the spam filter. Reasons for getting messages marked as spam vary, but usually there's little the sender can do about it. In this case, you should take the address that the mail was coming from and add it to your whitelist (see Customizing SpamAssassin, below).

When you have a "false positive", you will see the message in your Junk Mail folder is actually a report, listing the reasons SpamAssassin thought it was spam. The real message appears as an attachment.

Tip: If you use the Groupwise client, you can extract the real message from the spam report by dragging the original message from the attachments pane of the spam report to the folder you want to put the message in. Then you can delete the spam report.

Customizing SpamAssasssin

Several types of customization on the spam filter are possible. First, you can change the number of spam points required to mark a message as spam, called your spam threshold. Second, you can add email addresses to your whitelist or blacklist. Finally, you can change the subject tag. To perform any or all of these customizations, go to http://stopspam.messiah.edu and enter your username and password at the prompt.

Changing the "spam threshold"

This is the entry marked Required Hits on the customization page. Decreasing the number will let SpamAssassin catch more spam, but you may experience more false positives. Increasing the number will make SpamAssassin catch less spam, but will reduce the number of false positives.

Whitelisting Addresses

Your whitelist is a list of email addresses that always sends legitimate mail. Any mail coming from an address on this list will never be marked as spam. You could put your family and friends' email addresses on this list so you never miss an email from them.

Tip: If a friend sends you an email and it is marked as spam, put that friend's email address in your whitelist so that additional email from that person will not get marked as spam.

Blacklisting Addresses

Your blacklist is a list of email addresses that always sends unwanted email. Any mail coming from an address on this list will always be marked as spam. If you get promotional and marketing items from companies you have done business with, it probably will not get marked as spam without putting the addresses on the blacklist.

You cannot catch Messiah Mass Emails with the blacklist. The spam filter only operates on email coming from off-campus and since the Mass Emails originate from on-campus they are not scanned by the spam filter.

Changing the Subject Tag

You can customize what text is added to the Subject line of emails that are considered spam. In addition, you can have SpamAssassin insert information specific to each spam in the subject line. The complete list of tags that can be inserted are listed on the customization page.

Training the Spam Assassin

One of the methods that SpamAssassin employs to filter spam is Bayesian spam filtering. This method words by learning what each user's normal mail and their typical spam looks like. This method can be very effective, but requires giving SpamAssassin feedback when it makes a mistake.

So, if SpamAssassin makes a mistake, you should tell it. Here's how:

Teaching SpamAssassin when it lets a spam through

If a spam message arrives in your Inbox, forward it, as an attachment, to learnspam@messiah.edu.

Teaching SpamAssassin when it marks a regular message as spam

If a non-spam message got marked as spam (i.e. it was filed in your Junk Mail folder), forward it, as an attachment, to learnham@messiah.edu (that's ham instead of spam).

Within a few minutes, you should get an auto-response confirming that it learned from the message you forwarded it.