Web-based Email Clients that Are Safe
Many people use the most popular free mail services such as Hotmail, Yahoo, and so on. Those services currently don't offer the capability to turn off HTML emails. For those people who want to make their email accessible via the Web, there are several freely available clients that work with the Internet standards POP3 or IMAP. This means you can easily replace the troublesome Outlook Web Access with something safer and easily modifiable.
SquirrelMail (http://www.squirrelmail.org/) is a nice, lightweight, Web-based email client. The recently released 1.2.x series allows the administrator to enable or disable HTML email viewing by default, and, if enabled, includes an HTML view that strips out the JavaScript, meta tags, and any images/documents that were not included in the email itself. SquirrelMail is extensible through the use of plug-ins that change or enhance the behavior and features of SquirrelMail. This allows the administrator decide how much is necessary.
IMP (http://horde.org/imp/), the Internet Mail Program, is another Web-based, fully featured email client that doesn't by default display HTML emails. IMP is part of the Horde Project, which is a platform for Web-based applications for productivity, messaging, and project management.
If you own Microsoft Office, you can use Outlook (98, 2000, or XP). However, be absolutely certain to apply all the software and security updates. In and of itself, it does not make you immune to Web Bugs, but it does prevent many other associated problems, such as JavaScript and other scripting attacks. You can make it display ASCII only, but not in the simple "display only ASCII" manner you would expect from a piece of software that requires 135 megabytes of free disk space to install. Instead, it requires that you first turn off the preview pane (in View, Layout, uncheck Show preview pane). Then, every time you want to read a message, you need to right-click on the message, select Properties, Details, and Message source.
Microsoft shows the way: http://support.microsoft.com/directory/article.asp?ID=KB;EN-US;q165531.
If you only have Outlook Express installed on your computer, you are better off NOT using it and finding another email client such as Eudora (or even a different operating system whose focus is more on keeping your data safe rather than turning on features that make you a target).