In search of the perfect SPAM filter?

The apartment complex where I live has a post box area where the post man delivers mail for each resident. Some mail boxes have signs such as "No junk mail", "No advertising material" or "Addressed mail only". This is also the same area where our free local community newspaper is delivered. Whilst some residents simply don’t bother or have the time, others are out early to eagerly grab the latest edition to peruse over their morning coffee.

So what may you ask does this have to do with spam? Spam is the on-line equivalent of "junk" mail and as you can see in the above example, that junk mail/spam means different things to different people. They call it by different names and react to it quite differently. Even though the free newspaper has more adverts than the "junk mail" people view this differently.

The local news paper is also delivered to businesses in our area. While waiting for a doctor’s appointment in the waiting room of the medical centre, my wife read the news paper and found an advertisement for a great Christmas shopping coach trip that she will be enjoying with a group of friends. You can see that as is the case for the local drop sheet in the doctor’s waiting room, depending on the viewer’s circumstances, junk mail/spam may also mean different things at different times.

The fact is that email is a highly effective marketing tool and therefore as long as a percentage are responding positively there will be marketers prepared to deliver thousands of unsolicited mail messages.

So if we do not even have a clear definition of junk mail/spam then there is no such thing as the perfect spam filter.

At WebSuburb, our approach is to set out a suggested series of guideline steps. Each individual user can choose to implement as many or as few of these as they are comfortable with and which suit their individual circumstances.

Step 1 – Email addresses on your web site

To avoid unscrupulous harvesting of email addresses from your web pages you need to avoid using the “@” character. We suggest some of the following approaches:

• Don’t list you direct email address, rather use a generic address such as “info@...” Or support@.... This enables you to set up rules either on the server or in Outlook to better manage these emails.
• Obfuscate email addresses on your website. E.g. try “info at WebSuburb.com.au” This approach depends somewhat on the technical expertise of your target audience to correctly interpret the information. There is little point in losing your potential customers.
• Use an image of your email address. Even if the user picks the use of this technique, it doesn’t matter. There may even be an advantage to be had from search engine indexing if you use a good alt tag.
• Use an email obfuscating module for DotNetNuke sites.

It is unfortunate that all of these approaches sacrifice one great feature of HTML, the ability to enable to click on your email address to automatically activate the users email client to send you a message.

The optimal compromise in our opinion is to use the image of your email address and link this image to the contact us page containing a message form.

Step 2 – Catch all

The catch is an optional setting on the server that redirects any email addressed to a person not in the contact list to a specified address.

The advantage of this is that mail that is misspelt is handled without sending a rejection notice to the sender. I.e. it avoids the situation where a customer phones you to say “your email isn’t working!”

The disadvantages are:

• Confirms to spammers that an email address is valid and therefore sends a signal to send more mail.
• Effectively processing the email is dependant on an administrator in your business sifting through these emails and forwarding to the appropriate recipient. Given the significant amount of spam in existence this can be an onerous task.

Our recommendation is to switch the catch all functionality off.

Step 3 - Email server default settings

The default settings on the server categorise email into 4 groups:

• Mail
• Low probability of spam
• Medium probability of spam
• High probability of spam

Our recommendation is to automatically delete the email with a probability of Medium or High on the server. Be aware that there is a risk that genuine email may be deleted with this approach.

Step 4 – Outlook settings

Set up a rule in Outlook to automatically send all email containing “SPAM – Low” in the subject line to the junk mail folder.

To set up a new rule in Outlook:

Find an email in the inbox that has the words “SPAM-LOW” in the subject line. Right click on this item to bring up the menu and select the “Create Rule” option.

This will open a wizard form. Ensure that the “Subject contains” check box is ticked and edit the content of the text box to only reflect the words “SPAM-LOW”. Tick the check box, “Move e-mail to folder” and select the Junk Email folder. Click on the Advanced Options button and click the Next button twice until you reach the Exceptions screen.

Scroll down and tick the “Except if sender is in specified Address Book” option. This will automatically extend the processing rule in Step 2 dialog box. You will see that the word “specified” is underlined. Click on this hyper link.

Select the Contacts Address list and click on Add.

This is the last step of the wizard. Select the “Run this rule now …” and the “Turn on this rule” functions. Click on Finish

Outlook will now run the rule and move any e-mails that comply with the conditions that you have specified to the junk e-mail folder. Select the junk e-mail folder and review to see that you have not encountered any e-mails that have been falsely identified. The easiest way of adding contacts is to enable the preview pane in Outlook. One of my favourite subscriptions is to SearchEngineWatch, I certainly don’t want these in my junk mail folder so I select the email (marked 1 on the image) and in the preview pane right click on the email address and select the “Add to Contacts” menu option.

This automatically opens the Contacts information screen with the information pre-populated. Simply click on the Save and Close button. The contacts list has now been updated.

Well, that’s pretty much it for now. Outlook will continue to move all of these suspect e-mails to the junk mail folder. What you should do is to monitor the junk mail folder in Outlook for the next few days. Each time you find an email that has been falsely identified add the sender to your contacts list. You will find that the false positives soon dry up and that you will lose interest in reviewing the junk mail folder. Yes, simply delete it or switch on the automatically empty on close feature.

Step 5 - Email server heuristics

So you have executed all of the suggestions above but you are still being overwhelmed with spam. The next step is to adjust the heuristic settings on the email server.

If you wish to pursue this option then please contact us on the help desk as the heuristics settings affect all accounts on the server.

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