Reducing Junk Mail—Example: Configuring (OSX)


Depending on the Mail client that you are using, you may have as many as 4 methods of reducing SPAM:

  • Method 1—disable HTML display. Many email clients have the ability to display HTML formatted documents. One consequence of this is that your email address could be sent back to the sender of the document, which could open you up to more SPAM. Disabling this feature can reduced future SPAM. [setup]

  • Method 2—built-in junk-mail filters. Some mail clients have Junk mail filters built in. The Mac OS X Mail application and Entourage are examples of these kinds of mail clients. [setup]

  • Method 3—SpamAssassin. The central UOB mail server runs all messages through a SpamAssassin filter, which inserts new headers in the message. If the email is judged to be SPAM, one of these headers will be: X-Spam-Flag: YES. If you have setup a possiblespam mailbox for yourself in your area on the IMAP mail server, suspected SPAM will be sent to it. Computer Services provides instructions for activating SpamAssassin for Mulberry, the official UOB mail client. The instructions for Mulberry work equally well for Mail (Mac OS X) and probably for your favorite mail client as well. See UB Junk Mail Advice / SpamAssassin for Mulberry) for more information about SpamAssassin. [setup]

  • Method 4—client-configured filters. Email headers* and keywords may also be used to refine junk mail filtering on your computer. For example, if you have no possiblespam mailbox on the IMAP mail server, the X-Spam-Flag: YES header could still be used in conjunction with the filtering capability built into many email clients to filter out SPAM messages. Generally, the filters intercept and divert SPAM messages to a target junk mailbox, which you will need to create a junk mailbox prior to setting up a filter. [setup]

    *Note that most email clients hide arcane email headers, so you may never have seen the SPAM flag or other headers in a message. Nevertheless, filters can use these headers whether or not they are routinely visible. Somewhere in the settings, preferences or tools of your email client, you will be able to view the hidden headers. Here is an example of a SPAM message with all the headers displayed.

Setup and examples

Below are examples for implementing all of these methods in the Mac OS X Mail. The implementations detailed below should be analogous for any capable mail client (e.g., Entourage), but your mileage may vary depending upon your email client and operating system.

  • 1. Disabling HTML display in email messages

    The Display-HTML feature of most email clients can be disabled in the preferences/settings. In the Mac OS X Mail application go to Mail/Preferences/Viewing (see below) then disable the Display images and embedded objects in HTML messages:

  • 2. Junk Mail—built-in, junk-mail filters

    The Mac OS X Mail application has a junk mail filter built in (in the Mail application, see the menu Mail... item Junk Mail...). In training mode, the Junk Mail feature guesses which of your email message are junk mail and marks them. Selecting either marked or unmarked email messages allows you to either add or remove them from the list of junk mail. After you are satisfied that the Junk Mail feature is selecting correctly, go back to menu Mail... item Junk Mail... and set the Junk Mail feature to Automatic. Junk mail will be sent directly to a special mail box (Junk), which can be set to delete the message automatically if you wish (not recommended).

  • 4. Using Filters in Mail—an example using SpamAssassin information

    The instructions below show how to set up a filter for the Mac OS X Mail application that uses the SpamAssassin information that is inserted in all email headers by the UOB mail server (example SPAM message with all headers displayed). Note that if you are already using method 3 this particular filter will be completely redundant. Other headers or keywords could be used in like manner to create filters that might catch SPAM which has eluded SpamAssassin. Any PC or Mac mail client that can create filters can be set up in analogous fashion. In Mulberry the filters are called Rules. I have already created a filter that uses SpamAssassin. Here is how to make a filter.

    To create the SpamAssassin filter for the Mac OS X Mail application, go to Mail/Preferences/Rules (see below) then select the Edit button. I called the rule spamassassin, so it already appears below:

    You will need to create a header item called X-Spam-Flag (already done here) like is shown below. In Description give the rule a name (I used spamassassin below) Select the first popup menu for a list of options:

    In the pop-up menu ( X-Spam-Flag above) find the Edit Header List... item (the last item on the list blow):

    Create the Header: X-Spam-Flag (above), select the Add Header button (below) followed by OK.

    Set up the spamassassin filter as shown below. Then you are done.

maintained by: J. C. Schumacher

last revised: 6/5/03