iSchool Technology Knowledge Base

Article Overview:

Computing & Communication (C&C) provides an online tool to handle spam filtering (http://www.washington.edu/computing/email/spamfilter.html), however that tool only functions if your email is stored on the C&C server.  All iSchool faculty and staff, and some iSchool PhD. students have their email forwarded to an iSchool Exchange mail server.  This document describes how to implement spam filtering for iSchool faculty, staff, and PhD. students using Outlook and Exchange.

Spam Filter Concept:

The University of Washington spam filtering software adds a header to all incoming email messages that provides a probability rating that a message is spam or not.  The higher the probability rating, the more likely a message is spam.  We can take advantage of this rating to write an Outlook rule that will automatically move mail that has a high spam probability rating out of our Inbox and into an alternate folder. 

The unseen mail header looks like this:

X-Uwash-Spam: Gauge=XIIII

The Gauge variable is a quasi-Roman numeral.  In the above example the message has a 14% probability of being spam based on a software detection algorithm. The algorithm attempts to detect spam by looking for certain keywords in the message, by looking to see how the message was addressed, by checking if the message includes HTML markup, photographs, large text fonts, colors etc.   The algorithm is NOT perfect.  Real messages could have a high probability rating assigned to them if the message has characteristics similar to spam email. 

The Roman numeral used in the Gauge variable is not based on the traditional Roman numeral system.  For example if a message has a 60% chance of being spam the Gauge would read Gauge=XXXXXX, the system only uses X’s and I’s, X=10 and I=1. The spam filter does this on purpose so you can write a rule in your email client to filter messages based on the percentage you feel is a safe probability of being spam.  The more X's, the greater the probability a message is spam.
 

Solution Using Outlook 2002:

First you will need to create a folder to contain the purported spam. Bring up the new folder dialog window by selecting ‘File -> New -> Folder’ from the main Outlook menu bar, alternatively you can use the shortcut Ctrl+Shift+E.

After doing this you may be prompted with a dialog box asking if you want to add a shortcut to this folder to your Outlook bar. More than likely you will want to click on ‘No’; otherwise you can try this out and delete the shortcut later if you find it to be superfluous.

Now you will make the rule that will move the spam out of your Inbox. Open the Rules Wizard by selecting ‘Tools -> Rules Wizard’ from the main Outlook menu bar.

Select the ‘New…’ option.

Select ‘Start from a blank rule’.
You will see ‘Check message when they arrive’ highlighted, click ‘Next’.

Check the box with the message ‘with specific words in the message header’.
Next configure the rule by clicking the highlighted text ‘specific words’ in the rule description box. This step is shown in Figure 1 below.

Figure 1: Setting the rule conditions for specific words in message header

Next you will type Gauge=XXXXXXX into the space provided, as Figure 2 illustrates.  This tells Outlook that there must be seven X's (XXXXXXX) present in order for the message to be considered spam.  Seven X's is a 70% probability, which we have found to be a good starting point. 

If you find that a number of your regular messages are getting moved into the spam folder by mistake, increase the Gauge Roman numeral to 80% (XXXXXXXX).

On the other hand, if you are still receiving a large number of spam messages in your inbox and you want to be more aggressive in moving messages to the Junk Mail folder, then decrease this number, try 60% (XXXXXX). Remember that the lower you set the value, the more likely it will be that real messages (not just spam) will be moved into the Junk Mail folder. 

For the rule to work properly, just change the number of X's that you look for - do not try to use the I's to make fine adjustments.  Outlook is doing simple pattern matching and if you use characters other than X's in the Gauge, the rule will not work as you intend.

Figure 2: Search text for the rule

Click the 'Add' button and then ‘Ok’ to return to the Rules Wizard window, then click ‘Next’.

Now in the Rules Wizard window check the box that says ‘move it to the specified folder’ and click on the highlighted word ‘specified’ as Figure 3 demonstrates.

Figure 3: Moving the spam messages to a specified folder

You will be asked to choose a folder to move the filtered message to. Go ahead and select the 'Junk Mail' folder you created earlier and then click ‘Ok’.

This will return you to the Rules Wizard window, click ‘Next’ to continue.

At this point advanced users may want to create exceptions to the rule to allow certain email, which looks like junk, to bypass this rule. You can just click ‘Next’ to move on to naming your rule.

Once you give your rule a name (I used Spam), click ‘Finish’ and you will be taken to the last dialog box concerning your rule order.

More than likely you will want to just click ‘Ok’ and you are through. Again advanced users may want to think about the order in which this new rule will be processed, given that other rules exist.
 

Final Caveat:

You should periodically scan your Junk Mail folder in case a valid message is mistakenly placed there.  Remember the spam detection algorithm is far from perfect and if you do not check this folder you may miss important messages.

In addition to checking the spam folder for non-spam messages you should regularly purge old spam from your Junk Mail folder.  Open the Junk Mail folder so that you see all messages there.  Verify that there are no real messages that were moved there by mistake.  Then from the Outlook menu bar select 'Edit -> Select All'.  All of your Junk Mail messages will now be highlighted, select 'Edit -> Delete' to have these messages moved to your Deleted Items folder. 

As always, remember to occasionally purge your Deleted Items folder by right clicking on the Deleted Items folder and selecting 'Empty Deleted Items'.

A good name for the folder would be Junk Mail. Make sure the ‘Folder Contains’ box has ‘Mail and Post Items’ selected. You probably want to place the folder at the top of your mailbox tree, so click on the main ‘Mailbox’ container – there is a clock and house icon to its left.