why cant i get or send a message with outlook express i email on craig list and outlook pops up?

For Windows Vista users You can only use Firefox browser. for Yahoo as default email program, but you can still use Yahoo Messenger, in Internet Explorer.

Microsoft Windows Update disable the Add-ons in Windows Vista.

If you use Internet Explorer...

The tiny program that allows you to select Yahoo! Mail as the default email application for your PC is included as part of Yahoo! Toolbar version 7.2 and up for Internet Explorer (not Firefox).

If you don't have Yahoo! Toolbar v.7.2 or later for Internet Explorer installed, you’ll need to download it before proceeding with these instructions.

Here’s how to set your PC to open Yahoo! Mail when you click an email link on a web page.

1.From the "Start" pop-up menu in the lower left corner of your desktop, select "Settings" > "Control Panel".

2.In the Control Panel, select "Internet Options". This opens the "Internet Properties" window.

3.Click the "Programs" tab along the top.

4.Click the "E-mail" pull-down menu, and select Yahoo! Mail.

5.Click OK. Done!

If you're using Firefox 3...

1.At the top of Firefox 3, click Tools and select Options.

2.In the "Options" window, click Applications from the choices along the top.

3.Scroll down to "mailto", and click on it.

4.In the pull-down menu to the right of "mailto", click Use Yahoo! Mail.

5.Click OK at the bottom of the Firefox 3 window. You're done!