If you have to use email to send highly sensitive material to someone, convert the information into an image (e.g., a PDF, JPEG, TIFF, GIF, etc.). Doing so will add a significant layer of protection against malware that is programmed to automatically search email for anything looking like SSNs, passwords, bank account numbers, and the like. Likewise, if you insist on storing highly sensitive information on your computer, that should be stored as an image as well.
If you have Adobe Acrobat (or other PDF maker), you can easily convert a Word doc into a PDF image file. (Warning — be careful not to create a PDF with ”embedded text.” If you can search a PDF, then it’s got embedded text, ripe for the harvesting.) A quick and dirty (and free) way to convert a Word doc into an image is to use the “Print Screen” function to add an image of your screen to your Clipboard. You can then paste the screen image into another Word doc that you can save and email.
Note — when you save a doc as an image, you will no longer be able to search the body of the document. Keep that in mind when you name and store the doc on your PC.