One of the very best ways to keep spam out of your mailbox is to simply dispense with anything written in a non-Roman alphabet. Unless you work in those countries, any unexpected messages that arrive in your mailbox written in the Russian, Chinese, or Japanese alphabets are probably spam. To create rules to catch such messages, you need to explore the hidden world of headers.
Headers are codes that tell the e-mail application various useful things about the message; some of them are on display in the From, Subject, Date, and To fields at the top of the message as it is normally displayed. But there are other headers that are usually hidden from view. To see them, select the View Long Headers option in the Message section of the View menu (or press Command+Shift+H). When a message arrives in a non-Roman alphabet, take a look at the Content-Type header, and you’ll see a particular code there, for example, charset=iso-2022-jp for messages written in Japanese.
Figure 4 Headers contain valuable clues to the nature of incoming messages that can be used to filter spam.
To skim off these messages, all you need to do is create a rule that takes any messages with that Content-Type header and moves them to the Junk folder. However, when you open the criteria pull-down menu, you’ll see only the basic headers such as From and Subject, not the obscure ones such as Content-Type, so you’ll need to add this one manually. To do this, select the Edit Header List item at the bottom of the pull-down menu, and in the window presented, press the + symbol and then type Content-Type into the field that appears. You can now select Content-Type from the pull-down menu, just like any other header, and type in whatever text you want this rule to look for when it reads this particular header on incoming messages.
Figure 5 Create rules for non-Roman alphabets to quickly filter off foreign-language spam. Adding a color background helps you identify these messages at a glance when listed in the Junk or Trash folders.