Send your users to this free article so they can learn how to improve security by properly dealing with e-mail attachments: Help avoid computer viruses that spread through e-mail: Managing e-mail attachments in Outlook and Outlook Express
Many of the most common computer viruses and other malicious software are spread through e-mail attachments—the files that are sent along with an e-mail message. If a file attached to an e-mail message contains a virus, it's often launched when you open the file attachment (usually by double-clicking the attachment icon). No matter what e-mail program you use or what version of Windows you're running, you can help avoid some viruses by following a few basic rules. If you use the latest version of Outlook or Outlook Express and if you use the latest version of Windows, there are a few unique enhancements and default settings to help keep you from accidentally infecting your computer with a virus.